Solving “Found unknown categories […] in column” with sklearn OneHotEncoder

  • by
  • 1 min read

In this short blog post, I tackle an error related to a classic problem within machine learning: how to treat unseen categorical values and solve the “found unknown categories” error. Imagine you have a train and a test data set with the following values in a column: Train: [‘green’, ‘red’,… 

Solving “trend lines are not supported when marks are stacked” in Tableau

  • by
  • 2 min read

When you have a scatter plot in Tableau, you often want to add a trend line to indicate a relationship between two variables. However, sometimes it appears that it’s impossible: it’s greyed out and there is a tooltip that says “trend lines are not supported when marks are stacked”. Let’s… 

Undersampling a Pandas DataFrame

  • by
  • 2 min read

In a previous post, I explained how you can sample two Pandas DataFrame exactly the same way. In this blog post, I want to use that helper function to undersample your predictors and target variable. When you are working with an imbalanced data set, it’s often good practice to under-…