From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2011-02-02T06:46:59+09:00
Subject: Re: Returning a column vector from a 2D array

On Tue, Feb 1, 2011 at 8:53 PM, Jim Carter <jcarter@leupold.com> wrote:
> I have a @data_array variable, which is a 2 dimensional array.  If I
> run a @data_array.inspect, I get the entire 2D array in string form
> reporting back to me.
>
> But I want to pick off a specific column, ie., create a column vector
> from one of the columns on the array.  If I do something like
> @data_array.length, I get an undefined method length, probably because
> @data_array simply reference the Array ID??  If I do an
> @data_array.inspect.length, this appears to give me the number of
> elements in the complete array versus the actual length of the array.
> I need to know the length, to read back a vector (I believe).
>
> Is there already a method existing to do this, or do I need to go down
> the road of determining 2d array length, to read back a specific column
> of a 2d array through a looping structure?

Can you show some code? Are you using a specific 2d array from a
library or are you using an array of arrays?
If @data_array is referencing an object and not nil, can you show us
the ouput of puts @data_array.class ?
If the error you are getting mentions NilClass, you are probably not
assigning anything to @data_array.

Jesus.