Retaining variables in dcast in R

Question

I am using the dcast function in R to turn a long-format dataset into a wide-format dataset. I have an ID number, a categorical variable (CAT

Answer 1

For that, you need to add SEX to the ID side of your formula:

dcast(PC1, ID + SEX~CAT, value.var='AMT', fun.aggregate=sum, na.rm=TRUE)
# results in:

  ID    SEX  A  B  C
1  1 Female 46 22 31
2  2   Male 17 25 44

Things on the left hand side of the formula are kept as-is, things on the right-hand side are cast.