Initializing an NxN array


#1

Team,

What is the easiest way to initialize a square matrix?
For example, to initialize a 3x3 array elements to 0, I am doing what
you
see below. But I am not sure how to proceed if, for instance, I want a
NxN
array where N > 10 or a huge value?
I played a bit on IRB but could not find the way to do it easily.

irb(main):008:0> ary = Array.new(9,[0,0,0])
=> [[0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0],
[0, 0,
0], [0, 0, 0], [0, 0, 0]]

Thank you


#2

Ruby S. removed_email_address@domain.invalid wrote:

ary = Array.new(9,[0,0,0])

Tread carefully, Grasshopper:

ary = Array.new(9,[0,0,0])
ary[0][0] = “surprise!”
p ary

:slight_smile:

m.


#3

Ruby S. wrote:

Team,

What is the easiest way to initialize a square matrix?
For example, to initialize a 3x3 array elements to 0, I am doing what
you
see below. But I am not sure how to proceed if, for instance, I want a
NxN
array where N > 10 or a huge value?
I played a bit on IRB but could not find the way to do it easily.

irb(main):008:0> ary = Array.new(9,[0,0,0])
=> [[0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0],
[0, 0,
0], [0, 0, 0], [0, 0, 0]]

Thank you

Wouldn’t the best solution be:

require ‘Matrix’
a = Matrix.zero(3)

?

Assuming you actually want to use it for Matrix math and not as just a
2D array.

If you want a 2D array, I’d do ary = Array.new(3) {|row| Array.new(3)
{|col| 0}}


#4

Since * is defined on array, you can start with a 1x1 array and multiply
to the size you need.

n = 3;
ary = [[0]*n]*n

results in:
ary => [[0, 0, 0], [0, 0, 0], [0, 0, 0]]


#5

Evan F. wrote:

Since * is defined on array, you can start with a 1x1 array and multiply
to the size you need.

n = 3;
ary = [[0]*n]*n

results in:
ary => [[0, 0, 0], [0, 0, 0], [0, 0, 0]]

whoops! that has the same problem mentioned above:
irb(main):026:0> ary[0][0] = :foo; ary
=> [[:foo, 0, 0], [:foo, 0, 0], [:foo, 0, 0]]

I retract!


#6

On Thu, Mar 19, 2009 at 10:05, Ruby S. removed_email_address@domain.invalid
wrote:

For example, to initialize a 3x3 array elements to 0, I am doing what you
see below. But I am not sure how to proceed if, for instance, I want a NxN
array where N > 10 or a huge value?

N=3
Array.new(N) { Array.new(N,0) }

-m.


#7

On Thu, Mar 19, 2009 at 1:36 PM, Evan F. removed_email_address@domain.invalid
wrote:

whoops! that has the same problem mentioned above:
irb(main):026:0> ary[0][0] = :foo; ary
=> [[:foo, 0, 0], [:foo, 0, 0], [:foo, 0, 0]]

I retract!

Posted via http://www.ruby-forum.com/.

Thanks to all, your help is appreicated!