PSTricks and psmatrix

[Denis Girou]

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The following message is a courtesy copy of an article
that has been posted to comp.text.tex as well.

>>>>> "Jonas.Grave" == Jonas Grave <jonas_grave at yahoo.dk> writes:

    Jonas.Grave> Hello,
    Jonas.Grave> I have started using PSTricks with LaTeX. I don't understand why there
    Jonas.Grave> is a difference in alignment inside a psmatrix environment and outside
    Jonas.Grave> with respect to connecting nodes with arrows. The code at the end of
    Jonas.Grave> this post shows what I mean. Two diamond shaped boxes are drawn at the
    Jonas.Grave> same row but different column and connected with an arrow. But this
    Jonas.Grave> arrow does not start and end exactly at the tip of the diamonds. The
    Jonas.Grave> arrow is a bit below. However, drawing the same outside the psmatrix
    Jonas.Grave> environment, the arrow is exactly where it should be. What am I doing
    Jonas.Grave> wrong??

    Jonas.Grave> Jonas


    Jonas.Grave> \documentclass[a4paper]{article}

    Jonas.Grave> \usepackage{pst-node}
    Jonas.Grave> \usepackage{times}

    Jonas.Grave> \pagestyle{empty}

    Jonas.Grave> \begin{document}

    Jonas.Grave> \begin{psmatrix}
    Jonas.Grave>       \psdiabox{Diamond 1} & \psdiabox{Diamond 2}
    Jonas.Grave>       \ncline[arrowscale=2]{->}{1,1}{1,2}
    Jonas.Grave> \end{psmatrix}

    Jonas.Grave> \rput(1.8,-1){\dianode{A}{Diamond 1}}
    Jonas.Grave> \rput(6.8,-1){\dianode{B}{Diamond 2}}
    Jonas.Grave> \ncline[arrowscale=2]{->}{A}{B}

    Jonas.Grave> \end{document}

  The difference of position you notice is tiny and noticeable only with
careful verification, but it exist and become more evident if we increase
the scale factor. It give also a different result if we use a different string
like "Diamond q" in place of "Diamond 1".

  The reason of the difference between your two versions is not only that the
underlying mechanism is completely different. This is also because in the
second case you use a node of type \dianode and in the first case a node of
type \Rnode (which is the default for the "psmatrix" environment - see manual
page 27, file betadoc2.ps). And \Rnode is mainly provided to align strings,
using the "vref" parameter to position vertically it content (see manual
page 7, file betadoc1.ps). It is not well suited for the diamond boxes that
you use.

  So, in your case you must use, in the "psmatrix" environment, the "r" type
of nodes (which will use the \rnode macro), or the "dia" type if most of your
nodes have the diamond type.
  
\documentclass[a4paper]{article}

\usepackage[width=20cm]{geometry}
\usepackage{pst-node}

\pagestyle{empty}

\begin{document}

\Huge
\psset{unit=4,arrowscale=2}

\begin{psmatrix}
  \psdiabox{Diamond 1} & \psdiabox{Diamond 2}
  \ncline[linewidth=0.05]{->}{1,1}{1,2}
\end{psmatrix}

\begin{psmatrix}
  \psdiabox{Diamond q} & \psdiabox{Diamond q}
  \ncline[linewidth=0.05]{->}{1,1}{1,2}
\end{psmatrix}

\begin{psmatrix}[mnode=r]
  \psdiabox{Diamond 1} & \psdiabox{Diamond 2}
  \ncline[linewidth=0.05]{->}{1,1}{1,2}
\end{psmatrix}

\begin{psmatrix}[mnode=dia]
  Diamond 1 & Diamond 2
  \ncline[linewidth=0.05]{->}{1,1}{1,2}
\end{psmatrix}

\begin{pspicture}(0,-0.2)(4.4,0.2)
  \rput(1,0){\dianode{A}{Diamond 1}}
  \rput(3.4,0){\dianode{B}{Diamond 2}}
  \ncline[linewidth=0.05]{->}{A}{B}
\end{pspicture}

\end{document}

Denis Girou
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