Vectorize my thinking: Vector Operations in R

Question

So earlier I answered my own question on thinking in vectors in R. But now I have another problem which I can\'t \'vectorize.\' I know vectors are faster and loops slower, b

Answer 1

Strangely enough, learning to vectorize in R is what helped me get used to basic functional programming. A basic technique would be to define your operations inside the loop as a function:

data = ...;
items = ...;

leave_one_out = function(i) {
   data1 = data[items != i];
   delta = ...;  # some operation on data1
   return delta;
}


for (j in items) {
   delta.list = cbind(delta.list, leave_one_out(j));
}

To vectorize, all you do is replace the for loop with the sapply mapping function:

delta.list = sapply(items, leave_one_out);