[pstricks] Working with multiple data columns

[Herbert Voss]

Am 24.01.2010 04:08, schrieb Brandon Kuczenski:
> On Sat, 23 Jan 2010, Herbert Voss wrote:
> 
>> Am 23.01.2010 21:00, schrieb Brandon Kuczenski:
>>
>> http://tug.org/PSTricks/main.cgi?file=pst-plot/DataExamples#polarplot
>>
>> the last example shows how two values can be added
>> for a third plot.
>>
> 
> \makeatletter
> \pst at def{ScalePoints}<%
>   /y ED /x ED
>   counttomark dup dup cvi eq not { exch pop } if
>   /m exch def /n m 2 div cvi def
>   n { /RAD exch def  % save y as radius
>       dup            % xVal xVal
>       cos exch sin RAD mul y mul m 1 roll
>       RAD mul x mul m 1 roll
>       /m m 2 sub def } repeat>
> \makeatother
> 
> What does 'ED' mean?

exch def

> Thank you, this looks promising.. you are basically using ScalePoints to
> 'pre-process' the data queue-wise, so that x, y are turned into
> y*cos(x), y*sin(x).  This is basically what I want to do.

here is an example which plots the data (y3-y1)*cos(x) (y3-y1)*sin(x)
and saves the values in an external file data.dat, reads this file
at plots it with plotstyle dot. There is only a problem when running
the example from within a graphical user interface. Ghostscript
does't allow overwriting or creating files when it is not called
directly. However, run latex and dvips and then gs <file>.ps,
then everything should be fine.

Herbert

\documentclass{minimal}

\usepackage{pstricks-add}

\def\data{% x y1 y2 y3
1  45   67   89
2  46   66   87
3  47   62   88
4  44   61   80
5  42   52   72
}
\begin{document}
\begin{pspicture}(0,0)(10,10)
\begin{psgraph}[ticks=none](0,0)(-45,-5)(25,1){10cm}{10cm}
    % say we want to plot y3 - y1
    \listplot[linecolor=red]{
      /Pstdata (data.dat) (w) file def
      \data
      counttomark 4 div cvi /m exch def % m = num rows
      m { % x y1 y2 y3
        exch pop % ditch y2
        exch sub % y3 - y1
        exch dup RadtoDeg cos     % y x cos(x)
        3 -1 roll dup    % x cos(x) y y
        3 1 roll mul     % y x cos(x)*y
        3 1 roll RadtoDeg sin mul % cos(x)*y y*sin(x)
        2 copy
        exch
        20 string cvs Pstdata exch writestring
        Pstdata (\space) writestring
        20 string cvs Pstdata exch writestring
        Pstdata (\string\n) writestring
        counttomark cvi  2 roll % shift to front
      } repeat
    }
  \readdata{\Data}{data.dat}
  \listplot[showpoints=true,linecolor=blue,plotstyle=dots]{\Data}
\end{psgraph}
\end{pspicture}

\end{document}