March, 2010

Mar 10

R: Count unique items in a vector

Had to look this one up, so here it is:


Counts the number of distinct items in a vector in R.

Mar 10

Useful R link

Questions at stackoverflow about R:

Mar 10

R: "while" loops

R has regular while loops:

while (condition) {

Note that if you try to get help about while you get an error:


Error: unexpected ‘)’ in “help(while)”

Mar 10

>An error I got


Error in -value : invalid argument to unary operator

The problem was that I had the following code

fcnName <<-- value

Check out the extra dash typo, since R gives you no line numbers with the errors it took me a bit to track this down. Note the double << makes the assignment global in scope.

Mar 10

R tip iterating over list

To iterate over a list by key, value pair, do this:

for (name in names(myList)) {
    print(name)<br />
    print(myList[[name]])<br />

Note the double [[]] so you get just the value, not the pair.