Basically I'm looping through a matrix of arrays adding up the columns, but it stops right before the 2nd iteration of the 9.times loop. If I change y = 1 it will perform the action and stop at y = 2 and so on.
def new_feature(board)
x=0
y=0
vertical = []
while y < 9
9.times do
vertical << board[x][y]
x += 1
end
puts vertical.reduce(:+)
vertical = []
y += 1
end
end
You never reset x back to 0, so in the second while iteration your x starts with 9 where it finished last time, not 0. This makes board[9], which is presumably out of bounds and thus nil; and then nil[1] crashes your code.
Note that you can write 9.times do |x| ... end to have x count from 0 to 8 without any manual counting, since times passes the current iteration number into the block.
Also, a more Rubyish way to sum columns:
board.transpose.map { |row| row.reduce(&:+) }
