Multi-class logistic regression

We have seen several examples of binary logistic regression where the outcomes that we wanted to predict had two classes, such as a model predicting if a student will be admitted to the University (Yes or No) based on the previous exam results  or if a random Titanic passenger will survive or not.

Binary classification such as these are very common but you can also encounter classification problems where the outcome is a multi-class of more than two: for example if tomorrow weather will be sunny, cloudy or rainy; or if an incoming email shall be tagged as work, family, friends or hobby.

We see now a couple of approaches to handle such classification problems with a practical example: to classify a sky object based on a set of observed variables.
Data is from the Sloan Digital Sky Survey (Release 14).
For the example that we are using the sky object to be classified can be one of three classes: Star, Galaxy or Quasar.

The code is available also on a notebook in GitHub. Data is also available on GitHub. Continue reading “Multi-class logistic regression”