Re: save function

[Mike Miller]

On Tue, 8 Mar 2005, John W. Eaton wrote:

> On  8-Mar-2005, Robert A. Macy <address@hidden> wrote:
>
> | My two cents...
> |
> | Leave alone save function
> |
> | I have not experienced any problems with it.  If I don't
> | want the header, I throw it away.
>
> I think that's a good solution, but apparently some people want 
> bug-for-bug(*) compatibility.
>
> In any case, I would not do away with Octave's save format.  The 
> question is whether it is worth making the backwardly incompatible (for 
> Octave) but compatible (with Matlab) change so that -ascii works as it 
> does in Matlab.  We would move the current -ascii behavior to a 
> different option, perhaps -oct-ascii or -text or something.
>
> --------
>  * Though I suppose one person's bug is another's prized feature...


There are two distinct issues.  One is MATLAB compatibility.  The other is 
the annoying header lines.  The header lines can be useful, but there are 
many situations in which I do not want them.  I can tell that many other 
people often do not want them.  They are useful primarily when the data 
are to be read back into Octave.  When the data are going to another 
program, the header lines often have to be removed.

Robert Macy suggests that when he doesn't want the header lines, he throws 
them away.  That's what I do too.  For example, see the little perl script 
I wrote below.  In any collection of text files, it removes all initial 
consecutive lines that begin with '# ' (without the quotes) when the 
following line begins with a space.  You could name the script 
'remove_octave_headers', make sure the path to perl is correct for your 
system, then run it like this to fix all the Octave ascii output files in 
the default directory:

remove_octave_headers *.out

It replaces all of the original .out files with the headerless files.  If 
the file has multiple headers (multiple variables), it ignores the later 
headers (but that behavior could be changed).  I am assuming that a line 
beginning with a space always follows the last line of the header.

Sometimes I generate 10,000 data files from Octave, then I have to run 
this script on those 10,000 files to remove the headers.  It would be nice 
if I could just create the data without the header lines in the first 
place.

Regarding MATLAB compatibility - we don't want to do what MATLAB is doing 
(converting strings to numbers, deleting the imaginary parts of complex 
numbers, etc.).  How about having "save -ascii" produce a space-delimited 
text file with all of the requested variables in it, and no header?  This 
would be the sort of thing one would expect.  It would be more nearly 
compatible with MATLAB (not aligned in columns, but space delimited) and 
without the bug (dropping imaginary parts) or the weirdness (converting 
letters to numbers).  For storing a single matrix, it would do what I 
think most people would expect.  Don't we use the -ascii option to export 
to other programs?  If so, the header will usually get in the way.

Mike


------------------------begin script on next line----------------------
#!/usr/bin/perl -i -p

# This removes the initial header lines of an octave ascii data file

BEGIN{undef $/} s/(# [^\n]+\n)+ / /
------------------------end script on previous line--------------------



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