将data.frame中的所有列乘以第一列

Question

I need to multiply each column in a data.frame by the values in first column (classfactor).

This is my data.frame

sample classfactor 01.BA.V 01.BA.VG 01.BO.VG 01.PR.O 01.TO.VG 02.BA.O 02.BA.V
AB 0.730 0.000000000 0.000000000 0.000000000 0.000000000 0.000000000 0 0.00000000
AC 0.730 0.000000000 0.000000000 0.000000000 0.000000000 0.000000000 0 0.00000000
AB 0.002 0.000000000 0.000000000 0.000749929 0.000000000 0.000000000 0 0.00000000
CC 0.730 0.081599145 0.093453018 0.031247022 0.015987076 0.036212483 0 0.02537884
BB 0.730 0.000000000 0.000000000 0.000000000 0.000000000 0.000000000 0 0.00000000
AA 0.730 0.001533075 0.000108666 0.000000000 0.000364526 0.000241417 0 0.00006340

It has 146 rows and 155 columns.

I can't figure out how to do. Any suggestions?

Answer 1

If I'm not mistaken, you can do

df[-(1:2)] <- df[["classfactor"]] * df[-(1:2)]

where df is your data frame and the first column is sample ( classfactor is actually the second column).

Answer 2

Well, you could start with a loop.

for(i in 2:length(names(data.frame))) {
    data.frame[,i] <- data.frame[, 1] * data.frame[, i]
}

On a dataset as small as yours, this should be reasonably quick.