David,
Thanks very much!
That looks very elegant, if somewhat advanced. Can you point me to docs for the
Matrix class? I cant find it in my pickaxe book. 
How does a matrix/vector differ from an array?
Thanks again,
Christopher
···
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Subject: Re: Questions from a Ruby Newbie (file io and data structures)…
From: dblack@candle.superlink.net
Date: Tue, 28 Jan 2003 22:43:02 +0900
In-reply-to: 62951
Hi –
On Tue, 28 Jan 2003 christopher.j.meisenzahl@citicorp.com wrote:
I would like to read in a tab (or comma) delimited text file one line or one
item at a time. The input file might look like this:col1,col2,col3
a,b,c
d,e,f
g,h
jNote that there is not the same amount of data in each column. It could vary.
What is the best way to read this in from a file? When I’m done I would like
to
have all the items in col1 in an array, all the items in col2 in an array, and
so on.I’m sure this is a rudimentary task, but I would like to see the most elegant
ways in which Ruby permits something like this to be done.Any other thoughts very much appreciated!
Here’s a way to do this with the Matrix class. (It assumes
that there are no commas other than the field separators.)
require ‘matrix’
fh = File.open(“filename”,“r”)
m = Matrix[ *
Matrix[ *
fh.readlines.map {|l| l.chomp.split(‘,’) }
].column_vectors
]
The idea is to create a first matrix, based on the splitting of
lines on commas, and then to create a second matrix whose vectors
are the column vectors (i.e., rotated) of the first matrix.
This leaves you with a matrix, made up of Vectors, where each vector
is padded with nils if it’s shorter than whatever the longest one is.
For your sample data:
Matrix[Vector[“col1”, “a”, “d”, “g”, “j”], Vector[“col2”, “b”, “e”,
“h”, nil], Vector[“col3”, “c”, “f”, nil, nil]]
David
–
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web: http://pirate.shu.edu/~blackdav
Christopher J. Meisenzahl CPS, CSTE
Senior Software Testing Consultant
Spherion
christopher.j.meisenzahl@citicorp.com
