geoHeil geoHeil - 1 year ago 124
Python Question

Reduce number of levels for large categorical variables

Are there some ready to use libraries or packages for python or R to reduce the number of levels for large categorical factors?

I want to achieve something similar to R: "Binning" categorical variables but encode into the most frequently top-k factors and "other".

Answer Source

Here is an example in R using data.table a bit, but it should be easy without data.table also.

# Load data.table

# Some data
dt <- data.table(type = factor(sample(c("A","B","C"), 10e3, replace = T)),
                 weight = rnorm(n = 10e3, mean = 70, sd = 20))

# Decide the minimum frequency a level needs...
min.freq <- 3350

# Levels that don't meet minumum frequency (using data.table)
fail.min.f <- dt[, .N, type][N < min.freq, type]

# Call all these level "Other"
levels(dt$type)[fail.min.f] <- "Other"