how to remove multiple columns in r dataframe?

Question

I am trying to remove some columns in a dataframe. I want to know why it worked for a single column but not with multible columns e.g. this works

album2[,5]<- NULL

this doesn't work

album2[,c(5:7)]<- NULL
Error in `[<-.data.frame`(`*tmp*`, , 5:7, value = NULL) : 
replacement has 0 items, need 600

This also doesn't work

for (i in 5: (length(album2)-1)){
 album2[,i]<- NULL
}
Error in `[<-.data.frame`(`*tmp*`, , i, value = NULL) : 
new columns would leave holes after existing columns

Answer 1

Basic subsetting:

album2 <- album2[, -5] #delete column 5
album2 <- album2[, -c(5:7)] # delete columns 5 through 7