[pstricks] psgraph for non-integral axis lengths

[Alan Ristow]

Hi,

The psgraph macro has worked very well for me when the lengths of my
axes are whole numbers. For small axes, however, it has had problems.
Below I have a minimal example that illustrates the problems for a
y-axis of length 0.4. If I am not mistaken, this is expected behavior
resulting from the use of a non-integral divisor in \pst at divide (or,
more accurately, the limited fixed-point arithmetic capabilities of
TeX).

What I would like to know is: (1) Am I correct about this being the
expected behavior? (2) I can partially override psgraph's calculation of
\pst at xunit and \pst at yunit (see example 2 below), but is there a way to
completely override it? (3) Is my workaround using \pstScalePoints (see
example 3 below) the most expedient way to address this issue, or am I
missing something simpler?

I confess I haven't done an exhaustive search of the pstricks-add
documentation or www.pstricks.de, but it might be helpful to add an
example of how best to handle a situation like this to one or both of
them.

Alan



\documentclass{article}
\usepackage{pstricks}%
\usepackage{pstricks-add}%
\usepackage{filecontents}%

\begin{filecontents*}{test.d}
  0.0 0.2
  1.0 0.35
  2.0 0.38
  3.0 0.22
  4.0 0.15
  5.0 0.21
\end{filecontents*}

\pagestyle{empty}

\begin{document}

	% Example 1. Grid shows where frame borders and axis labels *should*
	% be placed, but axis is clearly longer than it should it be in the
	% y-direction.

  \begin{figure}[h]
    \psgrid[xunit=0.8in,yunit=0.5in,griddots=10,gridlabels=0,%
      gridcolor=gray,subgriddiv=0](5,4)%
    \begin{psgraph}[axesstyle=frame,tickstyle=bottom,Oy=0.0,Dy=0.1,%
        xyLabel={\small}](0,0)(5,0.4){4in}{2in}%
      \readdata{\data}{test.d}%
      \listplot{\data}%
    \end{psgraph}
  \end{figure}

	% Example 2. By adding yunit=5in to the psgraph options, the frame is
	% drawn correctly. However, the data are clearly plotted using an
	% incorrect yunit value.

  \begin{figure}[h]
    \psgrid[xunit=0.8in,yunit=0.5in,griddots=10,gridlabels=0,%
      gridcolor=gray,subgriddiv=0](5,4)%

\begin{psgraph}[yunit=5in,axesstyle=frame,tickstyle=bottom,Oy=0.0,Dy=0.1,%
        xyLabel={\small}](0,0)(5,0.4){4in}{2in}%
      \readdata{\data}{test.d}%
      \listplot{\data}%
    \end{psgraph}
  \end{figure}

	% Example 3. By changing the y-coordinate specification to 4 instead
	% of 0.4, adding dy=1 to the options list, and scaling the y data by
	% a factor of 10, the entire plot is drawn correctly.

  \begin{figure}[h]
    \psgrid[xunit=0.8in,yunit=0.5in,griddots=10,gridlabels=0,%
      gridcolor=gray,subgriddiv=0](5,4)%
    \begin{psgraph}[axesstyle=frame,tickstyle=bottom,Oy=0.0,Dy=0.1,%
        dy=1,xyLabel={\small}](0,0)(5,4){4in}{2in}%
      \pstScalePoints(1,10){}{}%
      \readdata{\data}{test.d}%
      \listplot{\data}%
    \end{psgraph}
  \end{figure}

\end{document}