gnuplot-beta

{column,row}major of multiplot

[Shigeharu T. <sh...@ie...>]

shige 01/06 2005
----------------

In ChangeLog of CVS version: 

  2005-01-04  Ethan Merritt  <merritt@u.washington.edu>
  ...
     * docs/gnuplot.doc: Correct the documentation to say
     'set multiplot layout <rows>,<cols>' (rows/cols were reversed in the
     previous version, and mis-described in the example).

I think it is true. Moreover, I wonder the behavior of options 
{column,row}major are reversed. gnuplot.doc says:

  This grid is filled rows first or columns first depending on
  whether `rowmajor` or `columnmajor` ...

However, in columnmajor (default), first two graphs are placed in
the first "row" from left to right. Is it correct behavior ?

+========================================================+
 Shigeharu TAKENO     NIigata Institute of Technology
                       kashiwazaki,Niigata 945-1195 JAPAN
 sh...@ie...   TEL(&FAX): +81-257-22-8161
+========================================================+

Re: {column,row}major of multiplot

[Ethan M. <merritt@u.washington.edu>]

On Wednesday 05 January 2005 08:29 pm, Shigeharu TAKENO wrote:
> shige 01/06 2005
> ----------------
> 
> In ChangeLog of CVS version: 
> 
>   2005-01-04  Ethan Merritt  <merritt@u.washington.edu>
>   ...
>      * docs/gnuplot.doc: Correct the documentation to say
>      'set multiplot layout <rows>,<cols>' (rows/cols were reversed in the
>      previous version, and mis-described in the example).
> 
> I think it is true. Moreover, I wonder the behavior of options 
> {column,row}major are reversed. gnuplot.doc says:
> 
>   This grid is filled rows first or columns first depending on
>   whether `rowmajor` or `columnmajor` ...
> 
> However, in columnmajor (default), first two graphs are placed in
> the first "row" from left to right. Is it correct behavior ?

I think you are right, and the current behavior is incorrect.
I will interchange the behavior of the two options unless
someone here proposes a different solution.


Short answer
------------

Standard mathematical terminology for arrays is A[row,column],
so that "row" is the first index.

The standard definition of "column major" is
"elements that differ only in their first index are contiguous".
In other words, "the first index varies fastest".
So indeed "column major" means that successive entries should
fill one column before continuing in the next column.

Longer answer
-------------

Some programming languages (e.g. C) and some application
communities (e.g. image processing) choose instead to refer to
arrays as A[column,row].  That is, the words "row" and "column"
now correspond to the 2nd and the 1st index respectively.
In this case "column major" still means "1st index varies fastest"
but the 1st index is unfortunately called "column" rather than
"row".  I have no idea why this terribly confusing choice of terms
was introduced.

So gnuplot's current use of the word "columnmajor" may be
technically correct with regard to internal storage of C arrays.
But the user doesn't care about internal arrays, only about
the appearance of the output page. We should change it to match
the output page.


-- 
Ethan A Merritt       merritt@u.washington.edu
Biomolecular Structure Center
Mailstop 357742
University of Washington, Seattle, WA 98195

Re: {column,row}major of multiplot

[Daniel J S. <dan...@ie...>]

Ethan Merritt wrote:

>Longer answer
>-------------
>
>Some programming languages (e.g. C) and some application
>communities (e.g. image processing) choose instead to refer to
>arrays as A[column,row].  That is, the words "row" and "column"
>now correspond to the 2nd and the 1st index respectively.
>In this case "column major" still means "1st index varies fastest"
>but the 1st index is unfortunately called "column" rather than
>"row".  I have no idea why this terribly confusing choice of terms
>was introduced.
>  
>
>

I too wonder how that ever came about.  Whenever I program C arrays, I 
always test to make sure I'm indexing in the right fashion rather than 
go from memory.

>So gnuplot's current use of the word "columnmajor" may be
>technically correct with regard to internal storage of C arrays.
>But the user doesn't care about internal arrays, only about
>the appearance of the output page. We should change it to match
>the output page.
>

Exactly.

I'm sure this will effect Octave and perhaps others.  But I'd prefer 
this be fixed in Gnuplot.

Dan

Re: {column,row}major of multiplot

[Petr M. <mi...@ph...>]

> > In ChangeLog of CVS version:
> >
> >   2005-01-04  Ethan Merritt  <merritt@u.washington.edu>
> >   ...
> >      * docs/gnuplot.doc: Correct the documentation to say
> >      'set multiplot layout <rows>,<cols>' (rows/cols were reversed in the
> >      previous version, and mis-described in the example).
> >
> > I think it is true. Moreover, I wonder the behavior of options
> > {column,row}major are reversed. gnuplot.doc says:
> >
> >   This grid is filled rows first or columns first depending on
> >   whether `rowmajor` or `columnmajor` ...
> >
> > However, in columnmajor (default), first two graphs are placed in
> > the first "row" from left to right. Is it correct behavior ?
>
> I think you are right, and the current behavior is incorrect.
> I will interchange the behavior of the two options unless
> someone here proposes a different solution.

The original meaning of "{columns|rows}major" comes from the original
author. It ment "fill first all columns|rows". The documentation was
correct, when I was adding keywords "upwards" and "downwards". I did not
like the names "*major" very much, but there was no better proposal.

I agree to change the syntax from "layout <cols>,<rows>" to "layout
<rows,cols>", and to replace those confusing "*major" by "rows$first" and
"columns$first".

---
PM