Re: Transform list into matrix

[PhilipNienhuis]

AJ wrote
> 
> Hi everybody!
> 
> I am new in using Octave. I have been browsing list as to look for a
> solution to my problem, related to matrices, but I have not found an
> example helping me. My question is if it is possible to construct a matrix
> from one net list (like Pajek .NET). This is one example which I have:
> 
> A B 5
> A F 7
> A K 4
> A X 8
> B D 1
> B P 1
> B Z 9
> C L 6
> C O 2
> ...
> 
> The real list have around 2 million of rows and I would have to load from
> a TXT file. Is there a easy way to do all this?
> 
> 

2 million rows, 6 or 7 bytes per line incl. EOL, means about 12-14 MB.
Nothing much.
After parsing the file into tokens, you'll have maybe 100 MB or so in memory
(depending on chosen data type), still shouldn't be problematic although
Octave may become a bit slow.

I wouldn't know how to properly parse a Pajek file, but if you want your
data file in a 3 X N cell array (N = number of rows in file) from which you
can do further processing, you could easily do in Octave-3.6.0:

fid = fopen ("put_Pajek_file_name_here");
C = textscan (fid, "%s %s %s", "collectoutput", 1);
fclose (fid);

(of course assuming all lines of your data file have the same layout).

(BTW I hit some strread.m bugs while trying, I've added a fix to the bug
tracker #35418)

Philip


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