In R, I am stacking a data.frame like so: stack(preds[1:(ncol(preds)-4)])
This selects 1,000 columns, and stacks them all into a single column, while creating a second column which is a string, the name of the column that row originally came from.
I then combine the remaining columns I did not stack with cbind(), which are implicitly repeated since they do not have the same length as the stacked data.frame.
cbind(preds[ncol(preds)], preds[ncol(preds)-3], preds[ncol(preds)-2], preds[ncol(preds)-1], stack(preds[1:(ncol(preds)-4)]))
I am trying to replicate this in Rust using Polars, but cannot find any kind of stacking function. Do I just need to iterate over all the Series to be stacked, calling append(), and manually repeat the remaining columns and join those to the stacked one with with_columns()?
melt() is the built-in function for this purpose. Note that the current latest release, 0.27.2, is O(n^2). If you need it to be fast you will need to install from the master branch polars = { git = "https://github.com/pola-rs/polars" } to get the latest bug fix that makes it O(n).