Updating floating point number in animation

Question

I'm trying to have an animated tikz graph with floating point values. While I can use floating point values as parameters for the graph, I can't seem to find a way to do so for displayed equations. Below is a MWE using beamer. The green line is animated properly - but the parameter does not appear in simplified form. The blue line shows the parameter appearing the way I would like it to (as a simplified number) but it is not updated in the tikz picture, even though it is updated outside that picture.

\documentclass[12pt]{beamer}

\usepackage{animate}
\usepackage{fp}
\usepackage{tikz}

\begin{document}

\newcounter{step}   
\setcounter{step}{1}

\newcommand{\scalevalues}{ %
\FPmul{\scaled}{\thestep}{0.1}
\FPtrunc{\scaled}{\scaled}{1}
}

\scalevalues   
\scaled % will print 0.1 above picture

\begin{animateinline}[loop, poster = first, controls, palindrome]{10}
\whiledo{\thestep < 21}{
    \begin{tikzpicture}
    %\useasboundingbox (-1,-1) rectangle (5,5);
    %
    \draw[->] (-1,0) -- (5,0) node[anchor=west]{\color{gray}x};
    \draw[->] (0,-1) -- (0,5) node[anchor=south]{\color{gray}y};
    % 
    \draw[-, thick, blue] (\scaled,-1) -- (5,4) node[anchor=east]{$\scaled x $};
    \draw[-, thick, green] (0.1*\thestep,-1) -- (2,3) node[anchor=east]{$0.1*\thestep x $};
    \end{tikzpicture}
    \stepcounter{step}
    \scalevalues  
    \scaled % will print updated values below picture
    \ifthenelse{\thestep < 21}{
            \newframe
    }{
        \end{animateinline}\relax 
    }
}

\end{document}

Answer 1

You have to carry out the calculation somehow but TikZ don't quite get that it's a computation it has to perform. So you can make it obvious by

{$\pgfmathparse{0.1*\thestep}\pgfmathprintnumber[fixed,precision=1]\pgfmathresult x $}

in that node.