Converting R Factors into Binary Matrix Values

Question

I would like to convert my dataframe into a matrix that expands a single factor column into multiple ones and assigns a 1/0 depending on the factor. Fo

Answer 1

Let's call your data.frame df:

library(reshape2)
dcast(df,C2*C3~C1,fill=0,length)

  C2 C3 A B
1  1  1 1 0
2  3  4 0 1
3  3  5 1 0