Graphics, Figures & Tables ⇒ Tikz calculations

[mtanner]

I am writing some Tikz code to draw multiple ellipses within a rectangle. I want to change the fill color of the ellipses based on a counter. So the code I have is:

Code: Select all

\def\clr{ref};   % initial color
\def\count{0}; % counter

\foreach \col in {1,...,\numcols}
  {
    \foreach \row in {1,...,\numrows}
       {
         \pgfmathsetmacro{\count}{\count+1};
         % calculate position and dimension of an ellipse
         \ifthenelse{\count>6} {\def\clr{blue}} {};
         \draw[fill=\clr] .....  % draw the ellipse
       }
  }

The ellipses are always filled with red. I have tried variations of the code to change \clr, but never with any effect. What is wrong with my code?

I cannot confirm that the value of \count is actually being updated by \pgfmathsetmacro.

[Stefan Kottwitz]

Welcome to the forum!

Can you perhaps post the complete TikZ picture code, so we can test and fix it? Maybe it's caused because the calculation of \pgfmathsetmacro gives 1.0 for example, instead of 1. With code I could test and fix it (the code above is not compilable).

Stefan

[Stefan Kottwitz]

I guess \ifthenelse was not properly used. Hard to say without code that can be tested.

Anyway, now I got some time to complete your code to have a compilable example, and I fixed it. I made it easier using a classic LaTeX counter instead of pgfmath.

Code: Select all

\documentclass[margin=10pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{math}
\usepackage{ifthen}
\newcounter{count}
\begin{document}
\begin{tikzpicture} 
  \def\clr{red}% initial color
  \setcounter{count}{0}% initial counter 
  \foreach \col in {1,...,6}
  {
    \foreach \row in {1,...,3}
       {
         \stepcounter{count}
         \ifthenelse{\value{count}>6}{\def\clr{blue}}{}
         \draw[fill=\clr] (\col,\row) ellipse (1cm and 1cm);
       }
  }
\end{tikzpicture}
\end{document}

ellipse.png (11.56 KiB) Viewed 4866 times

Just for fun as I stumbled across this topic again. With compilable code I would have figured it out earlier.

Stefan