Logistic regression to predict absenteeism- approach

Business Problem:

In today environment there is a high competitiveness which increase pressure on employee. High competitiveness leads unachievable goals, which cause an employee health issues, and health issue will lead absenteeism of employee.

With a given dataset an organisation is trying to predict employee absenteeism.

What is absenteeism in the business context?

Absence from work during normal working hours, resulting in temporary incapacity to execute regular working activity.

Purpose Of Model:

Explore whether a person presenting certain characteristics is expected to be away from work at some points in time or not.

Dataset:

I have downloaded a data set from kaggle called ‘Absenteeism_data.csv’ which contain following information.

  • Reason_1 – A Type of Reason to be absent.
  • Reason_2 – A Type of Reason to be absent.
  • Reason_3 – A Type of Reason to be absent.
  • Reason_4 – A Type of Reason to be absent.
  • Month Value – Month in which employee has been absent.
  • Day of the Week – Days
  • Transportation Expense – Expense in dollar
  • Distance to Work – Distance of workplace in Km
  • Age – Age of employee
  • Daily Work Load Average – Average amount of time spent working per day shown in minutes.
  • Body Mass Index – Body Mass index of employee.
  • Education – Education category(1 – high school education, 2 – Graduate, 3 – Post graduate, 4 – A Master or Doctor )
  • Children – No of children an employee has
  • Pet – Whether employee has pet or not?
  • Absenteeism Time in Hours – How many hours an employee has been absent.

Following are the main action we will take in this project.

  1. Build the model in python
  2. Save the result in Mysql.
  3. Visualise the end result in Tableau

Python for model building:

We are going to take following steps to predict absenteeism:

Load the data

Import the ‘Absenteeism_data.csv’ with the help of pandas

Identify Independent Variable i.e. identify the Y:

We have to be categories and we must find a way to say if someone is ‘being absent too much’ or not. what we’ve decided to do is to take the median of the dataset as a cut-off line in this way the dataset will be balanced (there will be roughly equal number of 0s and 1s for the logistic regression) as balancing is a great problem for ML, this will work great for us alternatively, if we had more data, we could have found other ways to deal with the issue for instance, we could have assigned some arbitrary value as a cut-off line, instead of the median.

Note that what line does is to assign 1 to anyone who has been absent 4 hours or more (more than 3 hours) that is the equivalent of taking half a day off initial code from the lecture targets = np.where(data_preprocessed[‘Absenteeism Time in Hours’] > 3, 1, 0)

Choose Algorithm to develop model:

As our Y (Independent variable) is 1 or o i.e. absent or not absent so we are going to use Logistic regression for our analysis.

Select Input for the regression:

We have to select our all x variables i.e. all independent variable which we will use for regression analysis.

Data Pre-processing:

Remove or treat missing value

In our case there is no missing value so we don’t have to worry about missing value. Yes, there are some columns who is not adding any value in our analysis such as ID which is unique in every case so we will remove it.

Remove Outliers

In our case there are no outliers so we don’t have to worry. But in general if you have outlier you can take log of your x variable to remove outliers.

Standardize the data

standardization is one of the most common pre-processing tools since data of different magnitude (scale) can be biased towards high values, we want all inputs to be of similar magnitude this is a peculiarity of machine learning in general – most (but not all) algorithms do badly with unscaled data. A very useful module we can use is Standard Scaler. It has much more capabilities than the straightforward ‘pre-processing’ method. We will create a variable that will contain the scaling information for this particular dataset.

Here’s the full documentation:

http://scikitlearn.org/stable/modules/generated/sklearn.preprocessing.StandardScaler.html

Choose the column to scales

In this section we need to choose that variable which need to transform or scale.in our case we need to scale  [‘Reason_1’, ‘Reason_2’, ‘Reason_3’, ‘Reason_4′,’Education’, pet and ‘children’], because these are the columns  which contain categorical data but in numerical form so we need to transform them.

What about the other column?

‘Month Value’, ‘Day of the Week’,  ‘Transportation Expense’,  ‘Distance to Work’,  ‘Age’, ‘Daily Work Load Average’, ‘Body Mass Index’ . These are the numerical value and their data type is int. so we do not have to transform them but will keep in our analysis.

Note:-

You can ask why we are doing analysis manually column wise?

Because it is always good to analyse data feature wise it gives us a confidence for our model and we can easily interpret our model analysis.

Split Data into train and test

Divide our data into train and test and build the model on train data set.

Apply Algorithm

As per our scenario we are going to use logistic regression in our case. Following steps will take place

Train the model

First we will divide the data into train and test. We will build our model on train data set.

Test the model

When we successfully developed our model then we need to test with a new data set which is testing data sets.

Find the intercepts and coefficient

Find out the beta values and coefficient from model.

Interpreting the coefficients

Find out which feature is adding more values in predictions of Y.

Save the model

Need to save the model which we have prepared so far. To do that we need to pickle the model.

Two executable file will save in your python directory one ‘model’ and the other is ‘scaler’

To save your .Ipnyb file in form of executable, save the same as .py file.

Check Model performance on totally new data set with same features.

Now we have a totally new data set which has same feature as per previous data set but contain different values.

Note – To do that your executable file ‘model’, scaler’ and ‘.py’ file should be in same folder.

Mysql for Data store

Save the prediction in data base (Mysql)

It is always good to save data and prediction on centralised data base.  So create a data base in mysql and create a table with all field available in your predicted data frame i.e ‘df_new_obs’

Import ‘pymysql’ library to make connection between ipynb notebook and mysql.

Setup the connection with user name and password and insert the predicted output values. In the data base.

Tableau for Data visualization

Connect the data base with Tableau and visualize the result

As we know tableau is a strong tool to visualise the data. So in our case we will connect our database with tableau and visualise our result and present to the business.

To connect tableau with my sql we need to take following steps.

  • Open the tableau desktop application.
  • Click on connect data source as mysql.
  • Put your data base address, username and password.
  • Select the data base.
  • Drag the table and visualize your data.

Network Intrusion Detection

In this case study we need to predict anomalies and attacks in the network.

Business Problem:

The task is to build network intrusion detection system to detect anomalies and attacks in the network.

There are two problems.

  1. Binomial Classification: Activity is normal or attack.
  2. Multinomial classification: Activity is normal or DOS or PROBE or R2L or U2R .

Data Availability:

This data is KDDCUP’99 data set, which is widely used as one of the few publicly available data sets for network-based anomaly detection systems.

For more about data you can visit to http://www.unb.ca/cic/datasets/nsl.html

BASIC FEATURES OF EACH NETWORK CONNECTION VECTOR

  1. Duration: Length of time duration of the connection
  2.  Protocol_type: Protocol used in the connection
  3.  Service: Destination network service used
  4.  Flag: Status of the connection – Normal or Error
  5.  Src_bytes: Number of data bytes transferred from source to destination in single connection
  6.  Dst_bytes: Number of data bytes transferred from destination to source in single connection
  7.  Land: if source and destination IP addresses and port numbers are equal then, this variable takes value 1 else 0
  8.  Wrong_fragment: Total number of wrong fragments in this connection
  9.  Urgent: Number of urgent packets in this connection. Urgent packets are packets with the urgent bit activated.
  10. Hot: Number of „hot‟ indicators in the content such as: entering a system directory, creating programs and executing programs.
  11. Num_failed _logins: Count of failed login attempts.
  12. Logged_in Login Status: 1 if successfully logged in; 0 otherwise.
  13. Num_compromised: Number of “compromised’ ‘ conditions.
  14. Root_shell: 1 if root shell is obtained; 0 otherwise.
  15.  Su_attempted: 1 if “su root” command attempted or used; 0 otherwise.
  16.  Num_root: Number of “root” accesses or number of operations performed as a root in the connection.
  17. Num_file_creations: Number of file creation operations in the connection.
  18. Num_shells: Number of shell prompts.
  19. Num_access_files: Number of operations on access control files .
  20. Num_outbound_cmds: Number of outbound commands in an ftp session.
  21. Is_hot_login: 1 if the login belongs to the “hot” list i.e., root or admin; else 0.
  22. Is_guest_login: 1 if the login is a “guest” login; 0 otherwise .
  23. Count: Number of connections to the same destination host as the current connection in the past two seconds
  24. Srv_count: Number of connections to the same service (port number) as the current connection in the past two seconds.
  25. Serror_rate: The percentage of connections that have activated the flag (4) s0, s1, s2 or s3, among the connections aggregated in count (23 )
  26. Srv_serror_rate: The percentage of connections that have activated the flag (4) s0, s1, s2 or s3, among the connections aggregated in srv_count (24)
  27. Rerror_rate: The percentage of connections that have activated the flag (4) REJ, among the connections aggregated in count (23)
  28. Srv_rerror_rate: The percentage of connections that have activated the flag (4) REJ, among the connections aggregated in srv_count (24)
  29. Same_srv_rate: The percentage of connections that were to the same service, among the connections aggregated in count (23)
  30. Diff_srv_rate: The percentage of connections that were to different services, among the connections aggregated in count (23)
  31. Srv_diff_host_ rate: The percentage of connections that were to different destination machines among the connections aggregated in srv_count (24)
  32. Dst_host_count: Number of connections having the same destination host IP address.
  33. Dst_host_srv_ count: Number of connections having the same port number.
  34. Dst_host_same _srv_rate: The percentage of connections that were to the same service, among the connections aggregated in dst_host_count (32) .
  35. Dst_host_diff_ srv_rate: The percentage of connections that were to different services, among the connections aggregated in dst_host_count (32)
  36. Dst_host_same _src_port_rate: The percentage of connections that were to the same source port, among the connections aggregated in dst_host_srv_c ount (33) .
  37. Dst_host_srv_ diff_host_rate: The percentage of connections that were to different destination machines, among the connections aggregated in dst_host_srv_count (33).
  38. Dst_host_serro r_rate: The percentage of connections that have activated the flag (4) s0, s1, s2 or s3, among the connections aggregated in dst_host_count (32).
  39. Dst_host_srv_s error_rate: The percent of connections that have activated the flag (4) s0, s1, s2 or s3, among the connections aggregated in dst_host_srv_c ount (33).
  40. Dst_host_rerro r_rate: The percentage of connections that have activated the flag (4) REJ, among the connections aggregated in dst_host_count (32) .
  41. Dst_host_srv_r error_rate: The percentage of connections that have activated the flag (4) REJ, among the connections aggregated in dst_host_srv_c ount (33).

Attack Class:

Let’s develop a machine learning model for further analysis.

Logistic Regression-Theory

As these days in analytics interview most of the interviewer ask questions about two algorithms which is logistic and linear regression. But why is there any reason behind?

Yes, there is a reason behind that these algorithm are very easy to interpret. I believe you should have in-depth understanding of these algorithms.

In this article we will learn about logistic regression in details. So let’s deep dive in Logistic regression.

What is Logistic Regression?

Logistic regression is a classification technique which helps to predict the probability of an outcome that can only have two values. Logistic Regression is used when the dependent variable (target) is categorical.

Types of logistic Regression:

  • Binary(Pass/fail or 0/1)
  • Multi(Cats, Dog, Sheep)
  • Ordinal(Low, Medium, High)

On the other hand, a logistic regression produces a logistic curve, which is limited to values between 0 and 1. Logistic regression is similar to a linear regression, but the curve is constructed using the natural logarithm of the “odds” of the target variable, rather than the probability.

What is Sigmoid Function:

To map predicted values with probabilities, we use the sigmoid function. The function maps any real value into another value between 0 and 1. In machine learning, we use sigmoid to map predictions to probabilities.

S(z) = 1/1+e−z

Where:

  • s(z)  = output between 0 and 1 (probability estimate)
  • z = input to the function (your algorithm’s prediction e.g.  b0 + b1*x)
  • e = base of natural log

Graph

In Linear Regression, we use the Ordinary Least Square (OLS) method to determine the best coefficients to attain good model fit but In Logistic Regression, we use maximum likelihood method to determine the best coefficients and eventually a good model fit.

How Maximum Likelihood method works?

For a binary classification (1/0), maximum likelihood will try to find the values of  b0 and b1 such that the resultant probabilities are close to either 1 or 0.

Logistic Regression Assumption:

I got a very good consolidated assumption on Towards Data science website, which I am putting here.

  • Binary logistic regression requires the dependent variable to be binary.
  • For a binary regression, the factor level 1 of the dependent variable should represent the desired outcome.
  • Only meaningful variables should be included.
  • The independent variables should be independent of each other. That is, the model should have little or no multicollinearity.
  • The independent variables are linearly related to the log of odds.
  • Logistic regression requires quite large sample sizes.

Performance evaluation methods of Logistic Regression.

Akaike Information Criteria (AIC):

We can say AIC works as a counter part of adjusted R square in multiple regression. The thumb rules of AIC are Smaller the better. AIC penalizes increasing number of coefficients in the model. In other words, adding more variables to the model wouldn’t let AIC increase. It helps to avoid overfitting.

To measure AIC of a single mode will not fruitful. To use AIC correctly build 2-3 logistic model and compare their AIC. The model which will have lowest AIC will relatively batter.

Null Deviance and Residual Deviance:

  • Null deviance is calculated from the model with no features, i.e. only intercept. The null model predicts class via a constant probability.
  • Residual deviance is calculated from the model having all the features. In both null and residual lower the value batter the model is.

Confusion Matrix:

It is nothing but a tabular representation of Actual vs Predicted values. This helps us to find the accuracy of the model and avoid overfitting. This is how it looks like

So now we can calculate the accuracy.

True Positive Rate (TPR):

It shows how many positive values, out of all the positive values, have been correctly predicted.

The formula to calculate the true positive rate is (TP/TP + FN). Or TPR =  1 - False Negative Rate. It is also known as Sensitivity or Recall.

False Positive Rate (FPR):

It shows how many negative values, out of all the negative values, have been incorrectly predicted.

The formula to calculate the false positive rate is (FP/FP + TN). Also, FPR = 1 - True Negative Rate.

True Negative Rate (TNR):

It represents how many negative values, out of all the negative values, have been correctly predicted. The formula to calculate the true negative rate is (TN/TN + FP). It is also known as Specificity.

False Negative Rate (FNR):

It indicates how many positive values, out of all the positive values, have been incorrectly predicted. The formula to calculate false negative rate is (FN/FN + TP).

Precision:

It indicates how many values, out of all the predicted positive values, are actually positive. The formula is (TP / TP + FP)

F Score:

F score is the harmonic mean of precision and recall. It lies between 0 and 1. Higher the value, better the model. Formula is  2((precision*recall) / (precision + recall)).

Receiver Operator Characteristic (ROC):

ROC is use to determine the accuracy of a classification model. It determines the model’s accuracy using Area Under Curve (AUC). Higher the area batter the model. ROC is plotted between True Positive Rate (Y axis) and False Positive Rate (X Axis).

In below graph yellow line represents the ROC curve at 0.5 thresholds. At this point, sensitivity = specificity.