Usage of inject on yale NMatrix

yale_column_sum.rb

require 'nmatrix'

b = NMatrix.new([4, 3], [1, 2, 3, 4, 5, 6, 7, 7, 7, 8, 9, 10])
c = NMatrix.new([4, 3], stype: :yale, default: 0)
c[0,0] = 1
c[1,1] = 2
c[2,2] = 4
c[3,2] = 8

puts b
puts c

#try to get the sum of each column
column_sums_b = []
column_sums_c = []

b.cols.times do |i|
  #puts "B column: #{b.col(i)}" # these columns are NMatrix objects
  #puts "C column: #{c.col(i)}" # these columns are NMatrix objects as well
  column_sums_b << b.col(i).inject(:+) # this will return a number
  column_sums_c << c.col(i).inject(:+) # this will return concatenated arrays with some strange(?) numbers
end

#puts column_sums_b
#puts column_sums_c