\pgfmathprintnumber cannot parse my numbers

Question

I was trying to find a way to write numbers in a specific manner in tikz (I wanted to get rid of the ".0". See code below). I struggled for a certain time, until I found percusse's answer (I didn't know the int() function existed). Now I have a working solution for what I need.

However, during my search for the perfect formatting of the numbers, I stumbled upon this document. In section 92 - Number Printing (on page 945), the \pgfmathprintnumber and the \pgfkeys commands/macros and the format/precision option for \pgfkeys are described. It seemed to be a good idea, but for some reason, it didn't work. I still cannot figure out why it doesn't work. Here is a sample code:

\documentclass[10pt]{article}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
    \pgfkeys{/pgf/number format/.cd,fixed,precision=0} % "precision = 0" does not print the trailling zeroes

    \draw[domain=0:10,smooth,variable=\x,blue,samples=100] plot ({\x},{sin(\x * pi r)}); % Sine
    \draw (0, 0) node[left] {AC voltage};
    \draw[dashed] (0, 0) -- (10, 0);
    \foreach \x in {0, 2, ..., 10} { \draw[dashed] (\x, -1.25) -- (\x, 2); } % Vertical lines
    \foreach \x in {0, 2, ..., 8}
    {
        % Problematic line:
        \draw[<->] (\x, -1.2) -- node[below] {\pgfmathprintnumber{\x/2+1}} (\x + 2, -1.2); % This line doesn't work
%       \draw[<->] (\x, -1.2) -- node[below] {\pgfmathparse{int(\x/2+1)}\pgfmathresult} (\x + 2, -1.2); % This line works perfectly
    }

\end{tikzpicture}
\end{document}

The error I get is

! Package PGF Math Error: Could not parse input '0/2+1' as a floating point number, sorry. The unreadable part was near '/2+1'..

I tried to play around with \pgfmathprintnumberto and format/fixed zerofill=boolean, as described in the manual, but nothing seemed to work.

Thanks in advance!

Answer 1

You need to use \pgfmathparse for the computation and then \pgfmathprintnumber to print the result.

Here's your modified MWE:

\documentclass[10pt]{article}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
    \pgfkeys{/pgf/number format/.cd,fixed,precision=0} % "precision = 0" does not print the trailling zeroes

    \draw[domain=0:10,smooth,variable=\x,blue,samples=100] plot ({\x},{sin(\x * pi r)}); % Sine
    \draw (0, 0) node[left] {AC voltage};
    \draw[dashed] (0, 0) -- (10, 0);
    \foreach \x in {0, 2, ..., 10} { \draw[dashed] (\x, -1.25) -- (\x, 2); } % Vertical lines
    \foreach \x in {0, 2, ..., 8}
    {
        % Problematic line:
        \draw[<->] (\x, -1.2) -- node[below] {\pgfmathparse{\x/2+1}\pgfmathprintnumber\pgfmathresult} (\x + 2, -1.2); % This line doesn't work
    }

\end{tikzpicture}
\end{document}