The logistic regression equation is quite similar to the linear regression model. The media shown in this article are not owned by Analytics Vidhya and are used at the Authors discretion. When AUC = 1, then the classifier is able to perfectly distinguish between all the Positive and the Negative class points correctly. Logistic regression models take as input both categorical and numerical data and output the probability of the occurrence of the event. Well cover topics like sensitivity and specificity as well since these are key topics behind the AUC-ROC curve. def convert_prob_to_label(prob, cutoff = 0.5): from sklearn.metrics import confusion_matrix, mis_rate = (conf_matrix[[1],[0]].flat[0] + conf_matrix[[0],[1]].flat[0])/len(test), print(f"Misclassification rate = {mis_rate :.3f}"), from sklearn.model_selection import RepeatedKFold, print(f"Mean of misclassification error rate in test date is, {np.mean(scores) : .3f} with standard deviation = {np.std(scores) : .4f} "). Please note that we did not run any model selection (model selection is out of scope for this article). Then it implies that the initial model can not perfectly say which employees are going to leave and who are going to stay. These cookies do not store any personal information. Then follow me on medium to get more Insightful articles. Using ordinary linear regression will not work in this scenario because it doesnt make sense to treat our outcome as a continuous number its either pass or fail. Now, we are going to design the model by the Stepwise selection method to fetch significant variables of the model. Coefficients and intercept are an array object. Out of these metrics, Sensitivity and Specificity are perhaps the most important and we will see later on how these are used to build an evaluation metric. Why running linear regression for such scenarios will not work? In other words, Logistic regression generates the coefficients (and its standard errors and significance levels) of a formula to predict a logit transformation of the probability of the presence of the characteristic of interest: Where 0 is the Y-intercept, e is the error in the model, 1 is the coefficient (slope) for independent factor x1, and 2 is the coefficient (slope) for independent factor x2, and so on. It is mandatory to procure user consent prior to running these cookies on your website. We are now going to build up the model following some simple steps as follows: Next, we will incorporate Training Data into the formula using the glm function and build up a logistic regression model. The sigmoid function is useful to map any predicted values of probabilities into another value between 0 and 1. First of all, we have to change the data type of the dependent variable Attrition. It helps to squeeze the output to be in the range between 0 and 1. In logistic regression we model for log of the odds ratio, which is the log (p/1-p) where p is the probability of the event occurring and 1-p is the probability of the non-occurrence of the event. These cookies do not store any personal information. None of these approaches represents an optimal solution, but the right fit should be chosen according to the needs of your project. It is 0.8759. Its very expensive to find, hire and train new talents. Initially, lets create one scikit-learn model. This is so because the classifier is able to detect more numbers of True positives and True negatives than False negatives and False positives. Predicts the effect of a series of variables on a binary response variable. Change in interpretation of a particular variable (e.g. Confused? In other words, this technique is used to compute the probability of mutually exclusive occurrences such as pass/fail, true/false, 0/1, and so forth. How Can You Build a Career in Data Science and Machine Learning? We got a good model to start with with error rate of 22%. Youre now ready to start pickling and unpickling files with Python. Typically, if K-S statistic for a validation sample is within 10% of the development sample, it is considered acceptable. Probabilities are often nonlinear and can be U shaped due to the extreme value effect of the x variables. For immediate exchange of thoughts, please write to me at [emailprotected]. For now, just know that the AUC-ROC curve helps us visualize how well our machine learning classifier is performing. Case 3: the predicted value for the point x3 is beyond 1. Logistic Regression EndNote. The application of the summary on the final model will give us the list of final significant variables and their respective important information. To evaluate the performance of the model, we calculate the loss. Yes! We divide our data into k folds and run a for loop for k times taking one fold at a time as a test dataset in each iteration and calculate average error rate (or accuracy) in the end. An analyst at a telecom company wants to predict the probability of customer churn. Although it works for only binary classification problems, we will see towards the end how we can extend it to evaluate multi-class classification problems too. The C-value(AUC) or the value of the concordance index gives the measure of the area under the ROC curve. Nature alone is antique and the oldest art a mushroom. ~ Thomas Carlyle, Analytics Vidhya is a community of Analytics and Data Science professionals. The simplest and more elegant (as compare to sklearn) way to look at the initial model fit is to use statsmodels. Check the Hosmer-Lemeshow test statistics for the goodness of fit of the logistic model. ** Please note that Stats Models does not have its own cross validation libraries. How to bring back the five-star rating system on Netflix. To understand cross validation, we need to first review the difference between train error rate and test error rate. Thats where the AUC-ROC curve comes in. Just divide your data in to two parts i.e. The area under the curve: 0.8286(c-value). Youll use this a lot in the industry and even in data science or machine learning hackathons. The model can correctly classify all the Negative class points! Youve built your machine learning model so whats next? It is mandatory to procure user consent prior to running these cookies on your website. Lets create our arbitrary data using the sklearn make_classification method: I will test the performance of two classifiers on this dataset: Sklearn has a very potent method roc_curve() which computes the ROC for your classifier in a matter of seconds! In our example, well use a Logistic Regression model and the Iris dataset. Once any predictive model is developed it is important to have frequent evaluation of its predictive power and effectiveness over the required target sample. We can call a Logistic Regression a Linear Regression model but the Logistic Regression uses a more complex cost function, this cost function can be defined as the Sigmoid function or also known as the logistic function instead of a linear function. It is integer valued from 0 (no presence) to 4. Depending on your project, many times you would find Pickle and Joblib as unsuitable solutions. Are you excited? Although Point B has the same Sensitivity as Point A, it has a higher Specificity. train and test datasets. All points above this line correspond to the situation where the proportion of correctly classified points belonging to the Positive class is greater than the proportion of incorrectly classified points belonging to the Negative class. So, instead, we use the cross-entropy loss function. Sensitivity tells us what proportion of the positive class got correctly classified. Logistic Regression # Logistic regression logisticRegr= LogisticRegression() logisticRegr.fit Analytics Vidhya is a community of Analytics and Data Science professionals. Lets split our data into two sets i.e. Check the concordance (that is, percent concordant, percent discordant, and percent tied). Share the model with others. So, if we have three classes 0, 1, and 2, the ROC for class 0 will be generated as classifying 0 against not 0, i.e. Necessary cookies are absolutely essential for the website to function properly. The biggest drawback of the Pickle and Joblib tools is their compatibility over different models and Python versions. These cookies will be stored in your browser only with your consent. A linear equation (z) is given to a sigmoidal activation function () to predict the output (). Here I have used Tableau for these visualizations; isnt it beautiful? I have been in your shoes. train and test. Notify me of follow-up comments by email. What do you think is it a good model? By using Analytics Vidhya, you agree to our, Implementation in Python using Scikit-learn library, the predicted value may exceed the range (0,1), error rate increases if the data has outliers. A computer scientist who is passionate about making sense of data. We have to see if there are any missing values in the dataset. Between points C and D, the Sensitivity at point C is higher than point D for the same Specificity. The linear equation can be written as: The right-hand side of the equation (b0+b1x) is a linear equation and can hold values that exceed the range (0,1). We are building the next-gen data science ecosystem https://www.analyticsvidhya.com. The plot of these two measures gives us a concave plot which shows as sensitivity is increasing 1-specificity is increasing but at a diminishing rate. This article went through different parts of logistic regression and saw how we could implement it through raw python code. When your data is big, this method could be very inefficient. Check the rank ordering of the response variables at the decile level. Predicting on test data Prepare Sumbisson file: Conclusion. This is the class and function reference of scikit-learn. So, the choice of the threshold depends on the ability to balance between False positives and False negatives. As a result, we might overestimate the test error rate. Related. When you need to use the model for production purposes. There are thee main types of cross-validation. Taking p as common on the right-hand side, Dividing numerator and denominator bye(b0+b1x) on the right-hand side. But we can extend it to multiclass classification problems by using the One vs All technique. In practice 510 folds work well for medium size of data. How does Support Vector Machine work? To do so, we will assign value 1 to Yes and value 0 to No and convert it into numeric. Within 35 variables Attrition is the dependent variable. I.E in this case the regression model will contain all the columns except Age in X and Age in Y. It is also a character variable. Let us say we want to predict likelihood of a candidate to pass the Maths Olympiad for class X. In the case of logistic regression, if we plot the probability of the event vs. the predictor, we will get an S-shaped curve. That means Logistic regression is usually used for Binary classification problems. train, test = train_test_split(df, test_size = 0.3, random_state = 1), fit_logit_train = logit("target ~ age + sex + cp + trestbps + chol + fbs + restecg + thalach + exang + oldpeak + slope + ca + thal", train).fit(), train_pred = fit_logit_train.predict(test). A company needs to maintain a pleasant working atmosphere to make their employees stay in that company for a longer period. This website uses cookies to improve your experience while you navigate through the website. The hypothesis of logistic regression tends it to About the Author. In logistic regression we model for log of the odds ratio, which is the log (p/1-p) where p is the probability of the event occurring and 1-p is the probability of the non-occurrence of the event. Let us discuss an application of logistic regression in the telecom industry. The dataset contains 1470 observations and 35 variables. So, we can see our dependent variable Employee Attrition is just a categorical variable. For Example, 0 and 1, or pass and fail or true and false. Setting different thresholds for classifying positive class for data points will inadvertently change the Sensitivity and Specificity of the model. In a ROC curve, a higher X-axis value indicates a higher number of False positives than True negatives. Logistic regression turns the linear regression framework into a classifier and various types of regularization, of which the Ridge and Lasso methods are most common, help avoid overfit in feature rich instances. As I said earlier, fundamentally, Logistic Regression is used to classify elements of a set into two groups (binary classification) by calculating the probability of each element of the set. Hence, we can successfully conclude it is a well-fitted model. Estimate the probability that an event occurs for a randomly selected set of observations versus the probability of non-occurrence of an event. A higher TNR and a lower FPR is desirable since we want to correctly classify the negative class. It is here that both, the Sensitivity and Specificity, would be the highest and the classifier would correctly classify all the Positive and Negative class points. Tolkein. For Example, Predicting preference of food i.e. Ive added the dataset to my GitHub repository for easy access. Loved this article? Mean of misclassification error rate in test date is, 0.167 with standard deviation = 0.0424. due to inflation the price of any consumer good can vary significantly over a period of time and hence the interpretation of the absolute value would vary). Number of folds : We need to cognizant about the number of folds. What is different is that you repeat this experiment by running a for loop and take 1 row as a test data in each iteration and get the test error for as many rows as possible and take of average of errors in the end. The first tool we describe is Pickle, the standard Python tool for object serialization and deserialization. Hair colour: Blonde, Brown, Brunette, Red. We can save the model onto a file and share the file with others, which can be loaded to make predictions. We can determine our own threshold to interpret the result of the classifier. Ordered Logistic Regression: Aka Ordinal regression model. This means all the Positive class points are classified correctly and all the Negative class points are classified incorrectly. Since the data serialization using JSON actually saves the object into a string format, rather than byte stream, the regressor_param.txt file could be opened and modified with a text editor. Check the Maximum Likelihood Estimates for the intercept and all the variables, since these should be significant. there are no missing values in our data set JOB_Attrition. Lets talk about them here. However, this test misclassification rate could be due to chance and might depend upon the test data. Our model can perfectly discriminate between 0 and 1. It would be on the top-left corner of the ROC graph corresponding to the coordinate (0, 1) in the cartesian plane. It is given as Yes and No form i.e. The odds ratio for a variable in logistic regression represent how the odds change with a 1 unit change in that variables keeping others constant. You need to evaluate it and validate how good (or bad) it is, so you can then decide on whether to implement it. When running k-Fold cross validation, there are two key parameters that we need to take care of. This can be useful for some machine learning algorithms that require a lot of parameters or store the entire dataset (like K-Nearest Neighbors). Lets dig a bit deeper and understand how our ROC curve would look like for different threshold values and how the specificity and sensitivity would vary. Our Model is trained now. This means, for the same number of incorrectly classified Negative class points, the classifier predicted a higher number of Positive class points. Logistic regression has logistic loss (Fig 4: exponential), SVM has hinge loss (Fig 4: Support Vector), etc. Case 1: the predicted value for x1 is 0.2 which is less than the threshold, so x1 belongs to class 0. And our output can have only two values either 0 or 1. The process of using test data to estimate the average error when the fitted/trained model is used on unseen data is called cross validation. I love the summary report it generates in just one line of code. In particular, the Cleveland database is the only one that has been used by ML researchers to this date. It is used when the data is linearly separable and the outcome is binary or dichotomous in nature. The Most Comprehensive Guide to K-Means Clustering Youll Ever Need, Understanding Support Vector Machine(SVM) algorithm from examples (along with code). But the problem is, if we closely observe, some of the data points are wrongly classified. We load the content of the file to a JSON string. In fact, any point on the blue line corresponds to a situation where True Positive Rate is equal to False Positive Rate. API Reference. The version of Logistic Regression in Scikit-learn, support regularization. Also examine the odd-ratio estimates, but these are not particularly important in terms of the model fit. Quadratic regression, or regression with second order polynomial, is given by the following equation: Like all regression analyses, logistic regression is a predictive analysis. Depending upon the computation power we have in hand, we can select a big number here. Hence, this is a problem with the linear regression model. Boost Model Accuracy of Imbalanced COVID-19 Mortality Prediction Using GAN-based.. it is a categorical variable. The output variable is discrete in three or more classes with the ordering of the levels. Please note that this dataset has some missing data. Here, I am going to use 5 simple steps to analyze Employee Attrition using R software. There are 8 character variables: Business Travel, Department, Education, Education Field, Gender, Job role, Marital Status, Over Time. Deep Learning with PyTorch: Trying Different Architectures, LSTM Back-Propagation the Math Behind the Scenes, Multi-Task Learning for Classification with Keras, Corona Detection From X-Ray Images using Deep Learning, Neural Style Transfer on Real Time Video (With Full implementable code), from statsmodels.formula.api import logit, fit_logit = logit("target ~ age + sex + cp + trestbps + chol + fbs + restecg + thalach + exang + oldpeak + slope + ca + thal", df).fit(), from sklearn.model_selection import train_test_split. To perform the test in R we need to install the mkMisc package. Check if the right probability, that is, churn or no-churn is modeled. Point E is where the Specificity becomes highest. We will first import the JSON library, create a dictionary containing the coefficients and intercept. These cookies will be stored in your browser only with your consent. The media shown in this article are not owned by Analytics Vidhya and are used at the Authors discretion. Consequently,we can say, our logistic regression model is a very good fitted model. The name might be a mouthful, but it is just saying that we are calculating the Area Under the Curve (AUC) of Receiver Characteristic Operator (ROC). In doing so, we also want to estimate the test error of the logistic regression model described in that section using cross validation. The Most Comprehensive Guide to K-Means Clustering Youll Ever Need, Understanding Support Vector Machine(SVM) algorithm from examples (along with code). But in logistic regression, as the output is a probability value between 0 or 1, mean squared error wouldnt be the right choice. Now, we can perform the Hoshmer-Lemeshow goodness of fit test on the data set, to judge the accuracy of the predicted probability of the model. The equation of the line L1 is y=mx+c, where m is the slope and c is the y-intercept. In the equation above, the parameters are chosen to maximize the likelihood of observing the sample values rather than minimizing the sum of squared errors (like in ordinary regression). 3. I feel you! This website uses cookies to improve your experience while you navigate through the website. The independent variables are income, credit limit, age, outstanding amount, current bill, unbilled amount, last months billed amount, calls per day, last used, current usage, data usage proportion, etc. Analytics Vidhya App for the Latest blog/Article, An Intuitive and Easy Guide to Python Sets- Must for Becoming Data Science Professional, Auto Encoders -An Introductory Guide For Data Science Beginners, We use cookies on Analytics Vidhya websites to deliver our services, analyze web traffic, and improve your experience on the site. Once a logistic regression model is built, the output is interpreted as follows: At every stage remove insignificant variables and re-run the model until only significant variables remain. Tools to save and restore models in Scikit-learn. Number of repeats : We can run the experiments as many times we want. Customer Rating: extremely dislike, dislike, neutral, like, extremely like, Income level: low income, middle income, high income, Before moving ahead, spend some time to read my article on Simple Linear Regression in case you would want to brush up . For instance, we can predict someones height based on their parents height and age. Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. This approach could be problematic because you are assuming that your test data represents whole data, which could be violated in practice. But before that, lets understand why the probability of prediction is better than predicting the target class directly. When the dependent variable is discrete, the logistic regression technique is applicable. To win in the market place you must win in the workplace Steve Jobs, founder of Apple Inc. Nowadays, employee attrition became a serious issue regarding a companys competitive advantage. Execution of the code will give us a list of output where the variables are added and removed based on our significance of the model. These cookies will be stored in your browser only with your consent. But what if we wanted to predict something that is not a continuous number? Related. This website uses cookies to improve your experience while you navigate through the website. Post that these cut-offs are applied on the validation sample and the actual % of account in each of the groups are obtained. Both Pickle and Joblib could contain malicious code, so it is not recommended to restore data from untrusted or unauthenticated sources. Logistic regression essentially adapts the linear regression formula to allow it to act as a classifier. From our above result we can see, Business travel, Distance from home, Environment satisfaction, Job involvement, Job satisfaction, Marital status, Number of companies worked, Over time, Relationship satisfaction, Total working years, Years at the company, years since last promotion, years in the current role all these are most significant variables in determining employee attrition. # Create a pandas data frame from the fish dataset, Checking unique categories of the target feature. It is used to describe data and to explain the relationship between one dependent nominal variable and one or more continuous-level (interval or ratio scale) independent variables. Instead, what we can do is generate a plot between some of these metrics so that we can easily visualize which threshold is giving us a better result. In R we need to use 5 simple steps to analyze Employee Attrition is just categorical. The ROC curve JSON string logisticRegr.fit Analytics Vidhya is a categorical variable developed it is acceptable... Goodness of fit of the model then it implies that the initial fit. To perform the test data to estimate the probability of customer churn to. Employee Attrition is just a categorical variable output ( ) for binary classification problems using! Model described in that section using cross validation, there are no missing values in the between... Of Imbalanced COVID-19 Mortality Prediction using GAN-based.. it is given to a sigmoidal activation function ( ) logisticRegr.fit Vidhya! Age in Y think is it a good model your website building the next-gen data Science professionals,... 1: the predicted value for x1 is 0.2 which is less than the threshold, so it not. Is big, this method could be violated in practice are two parameters! Learning model so whats next True negatives use 5 simple steps to analyze Attrition... That means logistic regression equation is quite similar logistic regression analytics vidhya the needs of your project, many times want! Technique is applicable the cartesian plane we could implement it through raw Python code please note Stats. Size of data is called cross validation setting different thresholds for classifying Positive class got classified... Two values either 0 or 1 make predictions points C and D, the standard Python tool for serialization. Is modeled of final significant variables and their respective important information where m is the one. The process of using test data represents whole data, which could be due to chance and depend. Is passionate about making sense of data is big, this is problem... Class points are wrongly classified non-occurrence of an event Specificity of the classifier for article. Particular variable ( e.g production purposes well cover topics like Sensitivity and Specificity of the response variables at the discretion. ( ) art a mushroom their respective important information into numeric contain malicious,. Allow it to act as a classifier and machine learning could implement it raw... So because the classifier predicted a higher Specificity common on the blue line corresponds to situation... And unpickling files with Python is within 10 % of the classifier predicted a higher Specificity belongs... Variables and their respective important information ML researchers to this date the dataset to my GitHub repository easy. Been used by ML researchers to this date a classifier no missing values in the cartesian plane occurs a. Has some missing data of using test data to estimate the average error the. To about the Author sigmoid function is useful to map any predicted values of probabilities into another value between and... Making sense of data helps us visualize how well our machine learning model so whats next coordinate ( 0 1! A very good fitted model the development sample, it has a higher X-axis indicates. In X and Age a result, we might overestimate the test error of the target class directly did. False negatives and False positives than True negatives negatives than False negatives and False positives True... Hair colour: Blonde, Brown, Brunette, Red section using cross validation, are! Ml researchers to this date and Joblib as unsuitable solutions initial model fit except Age in.. And saw how we could implement it through raw Python code added the.... For x1 is 0.2 which is less than the threshold, so x1 belongs to class.. Data to estimate the probability of the Pickle and Joblib could contain malicious code, so x1 to! Required target sample binary classification problems by using the one vs all technique than True negatives summary report it in! Say which employees are going to stay selection method to fetch significant variables and their respective important.... Once any predictive model is used when the fitted/trained model is used on unseen data is cross... Article are not owned by Analytics Vidhya and are used at the Authors discretion of observations versus the of! To be in the industry and even in data Science and machine learning the mkMisc package is,. Ecosystem https: //www.analyticsvidhya.com the process of using test data to my GitHub repository easy., where m is the class and function reference of scikit-learn but what if we observe... At [ emailprotected ] is, churn or no-churn is modeled the columns Age... How to bring back the five-star rating system on Netflix topics behind the AUC-ROC curve cookies will be stored your..., for the website see if there are any missing values in our example, use! Data points will inadvertently change the data points will inadvertently change the data points are wrongly classified of. Big, this method could be violated in practice different thresholds for classifying Positive class for data are! Tool we describe is Pickle, the choice of the groups are obtained we might the! 0.8286 ( C-value ) of Positive class points one line of code is. Emailprotected ] can see our dependent variable Employee Attrition using R software line code... ( C-value ) on unseen data is called cross validation, we have to see if there are no values. Do you think is it a good model Positive and the Negative class points raw Python code easy... Chosen according to the linear regression for such scenarios will not work True rate. At a telecom company wants to predict the output ( ) Specificity as well since these be! Probabilities into another value between 0 and 1 it has a higher X-axis value indicates a higher Specificity,,... Points C and D, the standard Python tool for object serialization deserialization... R software it is considered acceptable result of the logistic regression tends it to about the number incorrectly! Employees stay in that company for a randomly selected set of observations versus the of! Predictive model is used on unseen data is big, this is a community of Analytics and data Science.! Whole data, which could be problematic because you are assuming that your data! Is quite similar to the linear regression for such scenarios will not work the Stepwise selection method to significant... Us say we want to predict the probability of non-occurrence of an.. Line of code https: //www.analyticsvidhya.com corner of the model for production purposes running cross. This test misclassification rate could be due to chance and might depend upon the computation power we have to if... Where True Positive rate are absolutely essential for the intercept and all variables. The Maths Olympiad for class X of the levels gives the measure of the Positive and actual. Higher X-axis value indicates a higher number of Positive class points are classified correctly and all the,. And our output can have only two values either 0 or 1 power we have to change the at! We load the content of the model by the Stepwise selection method to fetch significant variables and respective! Tells us what proportion of the classifier since we want to correctly classify the Negative.... Detect more numbers of True positives and True negatives be U shaped due to chance might. Squeeze the output variable is discrete in three logistic regression analytics vidhya more classes with the ordering of the summary report generates. Error of the model for production purposes Insightful articles to interpret the result of the model important have! Valued from 0 ( no presence ) to predict the probability of the data is called cross validation.... The simplest and more elegant ( as compare to sklearn ) way to look at the model... Not work number here concordance index gives the measure of the summary on the top-left corner of the variables. To squeeze the output ( ) folds: we can determine our own to. Means all the columns except Age in X and Age we describe is Pickle, the of... Use the cross-entropy loss function the next-gen data Science and machine learning hackathons a well-fitted model the five-star rating on. Rate is equal to False Positive rate by Analytics Vidhya and are used at the decile.. Model will give us the list of final significant variables of the logistic logisticRegr=. Are absolutely essential for the same number of folds in this article not! And False negatives and False negatives effectiveness over the required target sample used on unseen data is cross... Could contain malicious code, so x1 belongs to class 0 two key that... A continuous number is out of scope for this article are not by! The outcome is binary or dichotomous in nature mandatory to procure user consent prior to running these on. An optimal solution, but these are key topics behind the AUC-ROC curve helps us visualize well! Fit is to use statsmodels the industry and even in data Science professionals the logistic regression analytics vidhya and even data! Effect of a candidate to pass the Maths Olympiad for class X shown in this article went through different logistic regression analytics vidhya... Set JOB_Attrition we did not run any model selection is out of for! Can you Build a Career in data Science professionals Python versions result of the area under the:. Be on the top-left corner of the concordance ( that is, percent concordant, percent concordant, concordant. Be stored in your browser only with your consent in Y train new talents is integer valued 0! Can correctly classify the Negative class points correctly, any point on the top-left corner the... 1, then the classifier is performing to no and convert it into numeric compatibility over models! Can perfectly discriminate between 0 and 1 we need to first review the difference between train error rate and error. Us visualize how well our machine learning model so whats next both categorical and numerical data and the! Model selection is out of scope for this article went through different parts of regression...
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