# Data mining algorithms: how many dummies?

There’s lots of posts on “k-NN for Dummies”. This one is about “Dummies for k-NN” Categorical predictor variables are very common. Those who’ve taken a Statistics course covering linear (or logistic) regression, know the procedure to include a categorical predictor into a regression model requires the following steps: Convert the categorical variable that has m categories, into m binary dummy variables Include only m-1 of the dummy variables as predictors in the regression model (the dropped out category is called the reference category) For example, if we have X={red, yellow, green}, in step 1 we create three dummies: D_red = … Continue reading Data mining algorithms: how many dummies?