[R] help converting code to a function

[r user]

I want to write a function that loads a data frame
from my hard drive, and then creates a new dataframe
that calculates the difference between column n and
column n+4, and them saves this new dataframe to my
hard drive, and finally, removes both the new and old
data frame from memory..

Here is the code I am using.

How do I convert this into a function that can be used
to perform the same process on any dataframe?


load ('c:/r_pit/sampledf.r')
w<-ncol(sampledf)
l<-nrow(sampledf)
sampledf_yychg <-
data.frame(matrix(data=NA,nrow=l,ncol=w-4))
for(j in 1:(w-4)) { sampledf_yychg[, j]<-sampledf[,
j]- sampledf[, j+4] }
save(sampledf_yychg, file='c:/r_pit/sampledf_yychg.r')
rm(sampledf, sampledf_sq, sampledf_yychg)