converting output of R's “by” command to data frame

Question

I\'m trying to use R\'s by command to get column means for subsets of a data frame. For example, consider this data frame:

> z = data.frame(         


        

Answer 1

Dealing with the by output can be really annoying. I just found a way to withdraw what you want in a format of a data frame and you won't need extra packages.

So, if you do this:

aux <- by(z[,2:5],z$labels,colMeans)

You can then transform it in a data frame by doing this:

  aux_df <- as.data.frame(t(aux[seq(nrow(aux)),seq(ncol(aux))]))

I'm just getting all the rows and columns from aux, transposing it and using as.data.frame.

I hope that helps.