Loop over a matrix
In your workspace, there's a matrix ttt
, that represents the status of a tic-tac-toe game. It contains the values "X", "O" and "NA". Print out ttt
to get a closer look. On row 1 and column 1, there's "O", while on row 3 and column 2 there's "NA".
To solve this exercise, you'll need a for
loop inside a for
loop, often called a nested loop. Doing this in R is a breeze! Simply use the following recipe:
for (var1 in seq1) {
for (var2 in seq2) {
expr
}
}
This is a part of the course
“Intermediate R”
Exercise instructions
Finish the nested for
loops to go over the elements in ttt
:
- The outer loop should loop over the rows, with loop index
i
(use1:nrow(ttt)
). - The inner loop should loop over the columns, with loop index
j
(use1:ncol(ttt)
). - Inside the inner loop, make use of
print()
andpaste()
to print out information in the following format: "On row i and column j the board contains x", wherex
is the value on that position.
Hands-on interactive exercise
Have a go at this exercise by completing this sample code.
# The tic-tac-toe matrix ttt has already been defined for you
# define the double for loop
for (___ in ___) {
for (___ in ___) {
print(___)
}
}