I need to extract columns in such a way where I am selecting one and then the next one which is 288 columns away. For example:
datanew <- data[, c(8, 296, 9, 297, 10, 298, 11, 299, 12, 300 etc)]
I need to do this up until 288, 576.
Could anybody suggest whether there is a quicker way to do this?
Something like
first_columns <- 8:288
next_columns <- first_columns+288
comb <- c(rbind(first_columns, next_columns))
This is the tricky part - since R stores matrices in column-first order, making a two-row matrix and then using c() to collapse it to a vector will make an interleaved vector of column numbers. (Checking with head(comb) shows 8 296 9 297 10 298 ... as requested.)
Then do data[, comb].
Another, somewhat more explicit way to do this:
comb <- rep(NA_real_, 2*(288-7)) ## set up vector (could also use numeric())
odds <- seq(1,length(comb), by=2)
evens <- seq(2, length(comb), by=2)
comb[odds] <- 8:288
comb[evens] <- comb[odds] + 288
You can take advantage of recycling and do something like this:
datanew <- data[, rep(8:288, each=2) + c(0, 288)]