for (i in 10:1) {
print(i)
}
As easy as that.
feature
18
Mar 10
R: Count unique items in a vector
Had to look this one up, so here it is:
length(unique(x))
Counts the number of distinct items in a vector in R.
17
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:
help(while)
Error: unexpected ‘)’ in “help(while)”
16
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.
16
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)
print(myList[[name]])
}
Note the double [[]] so you get just the value, not the pair.