Set PGFplots coordinate label using ifnum

Question

I can't overcome this little nasty issue. Using \ifnum I set labels position around the coordinates in my pgfplot. This works fine but :

I am only able to test if variable \coordindex is greater or smaller than a certain value. I want to be able to test if the index is equal to a number. Tex gives me this error, in case I use \ifnum\coordindex=0 at first.

Missing = inserted for \ifnum. \end{axis}

\documentclass{standalone}

\usepackage{pgfplots}
\pgfplotsset{compat=1.10}

\pgfplotsset{
    name nodes near coords/.style={
        every node near coord/.append style={
            anchor=center,                      % 
            name=#1\coordindex,                 % naming of npdes with running index
            alias=#1last,
        },
    },
    name nodes near coords/.default=coordnode
}

\begin{document}
\begin{tikzpicture}
    \begin{axis}[%
        width=\textwidth,
        height=.3\textheight,
        scale mode = scale uniformly,
        scale only axis,
        xmin=-200,
        xmax= 250,
        ymin=- 50,
        ymax= 400,
        axis x line = middle,
        axis y line = left,
        grid = none,
        xtick = {-200, -100, ...,300},
        ytick = {-100, 0, ...,400},
        minor tick num = 1,
        ytick align = outside,
        extra x ticks={0},
        extra x tick style={grid=major},
        xlabel={x / mm},
        ylabel={y / mm},
    ]

        \addplot+[
            color=orange,
            ultra thick,
            shape=circle,
            nodes near coords={},
            every node near coord/.append style={
               label={
                   [black!80, label distance=-1ex]
                   \ifnum\coordindex<1
                       5
                   \else
%                      \ifnum\coordindex=3
%                          -135
%                      \else
                           180-\coordindex*45
%                      \fi
                   \fi
                   :$p_{\coordindex}$
                }
            },
            name nodes near coords=p
        ]
        table{%
            0           0     
            -79.9393    236.8749 
            143.0014    350.0007
            143.0014    300.0000
            200.0008    300.0000
        };  
    \end{axis}
\end{tikzpicture}
\end{document}

I also tried with the ifthen package but had no luck. Please does anybody have a quick solution to this? What am I doing wrong? According to the document this shouldn't arise.

Maybe one of you also has a hint on how to print the ylabel the same way the xlabel is set; just at the top of and/or beside the y label.

I'd say that \newcommand\equals{=} in the preamble and \ifnum\coordindex\equals 0 should work. At least no error is raised. See http://tex.stackexchange.com/questions/214995/why-does-ifnum-not-work-inside-of-tikz-style-definitions — egreg, Dec 18 '14 at 14:10
You have to do the math somewhere else not where TikZ is looking for an anchor to place the label. — percusse, Dec 18 '14 at 14:13
@egreg This does it. ThumbsUp. Thanks so much for the wuick hint and the link, which explains what i actually going on. Didn't know about this. — goeck, Dec 18 '14 at 14:21

score 2 · Accepted Answer · edited Apr 13 '17 at 12:34

This is similar to Why does \ifnum not work inside of TikZ style definitions?, but the situation is different.

When processing label={...}, PGF looks for =; a workaround is thus hiding it:

        every node near coord/.append style={
           label={
               [black!80, label distance=-1ex]
               \ifnum\coordindex<1
                   5
               \else
                  \ifnum\coordindex\equals 3
                      -135
                  \else
                       180-\coordindex*45
                  \fi
               \fi
               :$p_{\coordindex}$
            }
        },

where \equals is defined in the preamble by

\newcommand{\equals}{=}

Another possibility:

        every node near coord/.append style={
           label={
               [black!80, label distance=-1ex]
               \numbercompare{\coordindex<1}
                 {5}
                 {\numbercompare{\coordindex=3}{-135}{180-\coordindex*45}}%
               :$p_{\coordindex}$
            }
        },

which requires

\usepackage{expl3}

\ExplSyntaxOn
\cs_set_eq:NN \numbercompare \int_compare:nTF
\ExplSyntaxOff

Maybe there is even a more elegant way to handle the discrimination than in this manner. The solution of the error is simple and elegant though! :-) — goeck, Dec 18 '14 at 14:32

Set PGFplots coordinate label using ifnum

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