[BioC] Help on alternative and efficient data frame manipulation

[Zhu, Lihua (Julie)]

Hi,

I have a data frame consisting of 5000 columns and 16000 rows. I would like
to convert all values x in column 4 to 5000 to 1 if x >0. The following code
works but it is very slow. Are there more efficient ways to modify large
number of entries in a data frame? Many thanks for your kind help!

id <- 4:ncol(mydata)
for (i in id) {mydata[mydata[,i]>0,i]=1}

Best regards,

Julie