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reading ascii matrix


From: John W. Eaton
Subject: reading ascii matrix
Date: Fri, 9 Feb 2001 09:53:58 -0600

On  9-Feb-2001, Ben Bauer <address@hidden> wrote:

| Info:
| Octave, version 2.1.9 (i686-pc-linux-gnu). 

2.1.9 is a really ancient development release.  You probably shouldn't
be using it.

| I have a plain ascii file of 2 columns and
| approx 2.8 million rows that I need to do some
| statistics on. In my octave script I have 
|   
|  for i=1:p
|   [a(i),b(i)]=fscanf(myfile,"%f %f","C"); 
|   ...

Unless you allocated space for a and b outside the loop, this code
will cause the vectors a(i) and b(i) to be resized every time through
the loop, and every element must be copied each time the vectors are
resized.  It will be slow and chew up a lot of memory.

Something like

  load ("name-of-myfile");

would probably be a lot faster.

jwe



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