I'm trying to make an animation in which increasingly small circles are drawn. I also want to draw a point of a hyperbola within each of those circles and this is where I'm having trouble. Specifically, I get the error

! Package PGF Math Error: Could not parse input '' as a floating point number,sorry. The unreadable part was near ''. (in '$25/(5-4/2').

I'm not sure what the problem is. Based on the error, my guess was that 25/3 being a floating point number what caused the issue, but trying

\addplot[only marks,red] (5-\nCoeff/2,$int(2500/(5-\nCoeff/2))/100$) node[above] {$y$};

results in essentially the same error. My MWE is the following

\documentclass{standalone}\usepackage{pgfplots, animate}\usetikzlibrary{calc}\pgfplotsset{compat = 1.17}\begin{document}   \begin{animateinline}[controls,palindrome]{1}      \multiframe{6}{nCoeff=4+-0.5}{            \begin{tikzpicture}            \begin{axis}               [               ticks=none,               axis equal,               axis x line=bottom,               axis y line=left,               xmin=0, xmax=10,               ymin=0, ymax=10,               ]              \draw[black, very thin, dashed] (5,5) circle [radius=\nCoeff];              \addplot[only marks, black] (5,5) node[above] {$x$};              \addplot[only marks,red] (5-\nCoeff/2,$25/(5-\nCoeff/2)$) node[above] {$y$};            \end{axis}         \end{tikzpicture}      }   \end{animateinline}\end{document}

• 3
  You are mixing thecalc library with the simple usage ofpgfmath in coordinates. Try\addplot[only marks,red] (5-\nCoeff/2,{25/(5-\nCoeff/2)}) node[above] {$y$}; — basically change your$ mark for a group to hide the parenthesis to the coordinate parser.

  Rmano

  – Rmano

  2025-04-23 13:02:09 +00:00

  CommentedApr 23 at 13:02

1 Answer1

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