Numbers as markers with \foreach and additional macro based on counter

Question

First issue

I would like to plot several curves using the \foreach command and have their number in the sequence as markers. Here is the code I came up with :

\documentclass{article}
\usepackage{pgfplots}
\usepackage{pgfplotstable}

\begin{document}
\begin{tikzpicture}
  \pgfplotstableread{
1 4   0.2  0.1
2 4.2 0.1  0.5
3 3.1 0.3  0.4
4 2.5 0.25 0.35
}\table

\begin{axis}
  \foreach \i in {1,2,3}
\addplot+[text mark={\i}, mark=text] table[x index=0, y index=\i]{\table};
\end{axis}
\end{tikzpicture}
\end{document}

and here is the result it raises :

My problem is that for some reason the text mark={\i} is stuck to 1.

A solution is to use the \pgfplotsinvokeforeach command (see my answer).

Second issue

But now if I need some other index computed from the counter using for instance

\pgfmathsetmacro{\j}{\i+1}% with the \foreach command

I would write

\pgfmathsetmacro{\j}{##1+1}% with the \pgfplotsinvokeforeach command

but this last one does not work. I think the problem is that the #1 is interpreted as if it is supposed to represend an argument of \pgfmathsetmacro. My attempt of doubling the hash did not solve this second issue.

Answer 1

For the updated problem you can use the math engine of PGF.

\documentclass{article}
\usepackage{pgfplots}
\usepackage{pgfplotstable}

\begin{document}
\begin{tikzpicture}
  \pgfplotstableread{
1 4   0.2  0.1
2 4.2 0.1  0.5
3 3.1 0.3  0.4
4 2.5 0.25 0.35
}\table

\begin{axis}
\pgfplotsinvokeforeach{1,2,3}{%
\addplot+[text mark={\pgfmathparse{int(#1+1)}\pgfmathresult}, mark=text] table[x index=0, y index=#1]{\table};};
\end{axis}
\end{tikzpicture}
\end{document}

Answer 2

The problem can be solved by using \pgfplotsforeach instead of \foreach

\documentclass{article}
\usepackage{pgfplots}
\usepackage{pgfplotstable}

\begin{document}
\begin{tikzpicture}
  \pgfplotstableread{
1 4   0.2  0.1
2 4.2 0.1  0.5
3 3.1 0.3  0.4
4 2.5 0.25 0.35
}\table

\begin{axis}
  \pgfplotsinvokeforeach{1,2,3}{%
\addplot+[text mark={#1}, mark=text] table[x index=0, y index=#1]{\table};};
\end{axis}
\end{tikzpicture}
\end{document}

I found it thanks to this question pgfplots: setlength inside foreach.