Plotmarks of TikZ are off by 0.05 in x-direction

Question

When I use Gonzalos Medinas' method in the link everything turns out fine except that my circles seems to be off by about 0.05 in the x-direction.

This is his code:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{plotmarks}

\begin{document}

\begin{tikzpicture}
\draw (0,-1)--(10,-1);
\node[mark size=3pt,color=red] at (0,-1) {\pgfuseplotmark{*}};
\node[mark size=5pt,color=blue] at (5cm,-1) {\pgfuseplotmark{triangle*}};
\node[mark size=4pt,color=olive] at (10cm,-1) {\pgfuseplotmark{square*}};

\draw[mark=*,mark size=3pt,mark options={color=olive}] plot coordinates {(0,-2)} 
  -- plot[mark=triangle*,mark options={color=blue}] coordinates {(5cm,-2)} 
  -- plot[mark=square*,mark size=4pt,mark options={color=red}] coordinates {(10cm,-2)};
\end{tikzpicture}

\end{document}

I use just a part of his code in another one of my plots: a slight modification (for changes see below)

\node[mark size=3pt,color=red] at (0,-1) {\pgfuseplotmark{*}};
\node[mark size=5pt,color=blue] at (2,-1) {\pgfuseplotmark{triangle*}};
\node[mark size=4pt,color=olive] at (1,-1) {\pgfuseplotmark{square*}};

He uses (e.g.)

\node[mark size=4pt,color=olive] at (10cm,-1) {\pgfuseplotmark{square*}};

while I use (no squares!)

\node[mark size=4pt,color=olive] at (1,-1) {\pgfuseplotmark{*}};

What is wrong here?

Answer 1

New answer

Paul Gaborit points out that the pgfmanual specifically mentions that pgf commands such as \pgfuseplotmark should not be used in situation, such as a node, where text is expected. Rather they should be in a pgfpicture (or tikzpicture) environment.

One (ugly) work around to your approach is then to write the node argument in pgfpicture environment:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{plotmarks}

\begin{document}

\begin{tikzpicture}
\draw (-1,0) -- ++(2,0);
\draw (0,-1) -- ++(0,2);
\node[mark size=5pt,color=blue,draw] at (0,0) {%
\begin{pgfpicture}
  \pgfuseplotmark{triangle*}
\end{pgfpicture}%
};

\end{tikzpicture}

\end{document}

I have drawn a rectangle around the node to show the spacing, compare with bad spacing demonstrated in the original answer below.

Better is to use the mark mechanism as intend in a plot of just one point:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{plotmarks}

\begin{document}

\begin{tikzpicture}
  \draw (-1,0) -- ++(2,0);
  \draw (0,-1) -- ++(0,2);
  \draw[color=blue] plot[mark=triangle*,mark size=5pt] (0,0);
\end{tikzpicture}

\end{document}

In your code this would give

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{plotmarks}

\begin{document}

\begin{tikzpicture}
\draw (0,0) -- ++(0,-3);
\draw (5cm,0) -- ++(0,-3);
\draw (10cm,0) -- ++(0,-3);

\draw (0,-1)--(10,-1);
\draw[color=red] plot[mark=*,mark size=3pt] (0,-1);
\draw[color=blue] plot[mark=triangle*,mark size=5pt] (5cm,-1);
\draw[color=olive] plot[mark=square*,mark size=4pt] (10cm,-1);

\draw[mark=*,mark size=3pt,mark options={color=olive}] plot coordinates {(0,-2)} 
  -- plot[mark=triangle*,mark options={color=blue}] coordinates {(5cm,-2)} 
  -- plot[mark=square*,mark size=4pt,mark options={color=red}] coordinates {(10cm,-2)};
\end{tikzpicture}

\end{document}

Original answer

Most of the plot mark definitions have an error in them with newlines not commented out. For example the triangle* is defined as:

\pgfdeclareplotmark{triangle*}
{%
  \pgfpathmoveto{\pgfqpoint{0pt}{\pgfplotmarksize}}
  \pgfpathlineto{\pgfqpointpolar{-30}{\pgfplotmarksize}}
  \pgfpathlineto{\pgfqpointpolar{-150}{\pgfplotmarksize}}
  \pgfpathclose
  \pgfusepathqfillstroke
}

Lines 3, 4 and 5 do not have the newline escaped and so insert a space in to the output, as you can see by drawing the box around the node:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{plotmarks}

\begin{document}

\begin{tikzpicture}
\draw (0,0) -- ++(0,-2);

\node[mark size=5pt,color=blue,draw] at (0,-1) {\pgfuseplotmark{triangle*}};

\end{tikzpicture}

\end{document}

Correcting these definitions, mostly found in pgflibraryplotmarks.code.tex gives in the original example:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{plotmarks}

\begin{document}

\begin{tikzpicture}
\pgfdeclareplotmark{triangle*}
{%
  \pgfpathmoveto{\pgfqpoint{0pt}{\pgfplotmarksize}}%
  \pgfpathlineto{\pgfqpointpolar{-30}{\pgfplotmarksize}}%
  \pgfpathlineto{\pgfqpointpolar{-150}{\pgfplotmarksize}}%
  \pgfpathclose
  \pgfusepathqfillstroke
}
\pgfdeclareplotmark{*}
{%
  \pgfpathcircle{\pgfpointorigin}{\pgfplotmarksize}%
  \pgfusepathqfillstroke
}

\draw (0,0) -- ++(0,-3);
\draw (5cm,0) -- ++(0,-3);
\draw (10cm,0) -- ++(0,-3);

\draw (0,-1)--(10,-1);
\node[mark size=3pt,color=red] at (0,-1) {\pgfuseplotmark{*}};
\node[mark size=5pt,color=blue] at (5cm,-1) {\pgfuseplotmark{triangle*}};
\node[mark size=4pt,color=olive] at (10cm,-1) {\pgfuseplotmark{square*}};

\draw[mark=*,mark size=3pt,mark options={color=olive}] plot
  coordinates {(0,-2)} 
  -- plot[mark=triangle*,mark options={color=blue}] coordinates {(5cm,-2)} 
  -- plot[mark=square*,mark size=4pt,mark options={color=red}]
  coordinates {(10cm,-2)}; 
\end{tikzpicture}

\end{document}

I have added vertical lines to show the alignment.