[Tex/LaTex] Print integer without fraction part

formattingpgfmathtikz-pgf

In a Tikz Figure, I'm doing some computation and want to print results as label of nodes.
The problem is that I only need the integer part of the number to print.

I tried with round() function. It round the values correctly but they are printed with .0

\begin{tikzpicture}
   \foreach \i in {1,2,3,4,5,6} {
      \pgfmathparse{round(\i*100/3) }
       \let\theIntINeed\pgfmathresult
       \draw (\i,0) node {\theIntINeed};
   }
 \end{tikzpicture}
 % Results: 33.0 67.0 100.0 133.0 167.0 200.0

Thank you in advance.

Best Answer

\pgfmathparse always saves its result with a decimal part. You can either use \pgfmathprintnumber{\pgfmathresult} in the node text to output the number, which will remove the .0 for integers, or do the calculation using \pgfmathtruncatemacro\mymacro{round(\i*100/3)}, which will save the result of the calculation without the decimal part, and then use \mymacro in the node text.

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[Tex/LaTex] Accessing the logic values of a TikZ coordinate

PGF has the \pgfmathprintnumber macro that allows you to print and format numbers, including rounding. To round to two decimal digits, you would use \pgfmathprintnumber[precision=2]{\pgfmathresult}, for example.

The unit vectors are stored in \pgf@xx (for the x-component of the x unit vector) and \pgf@yy (the y-component of the y unit vector). So your function could be shortened to

\makeatletter
\newcommand\xcoord[2][center]{{%
    \pgfpointanchor{#2}{#1}%
    \pgfmathparse{\pgf@x/\pgf@xx}%
    \pgfmathprintnumber{\pgfmathresult}%
}}
\newcommand\ycoord[2][center]{{%
    \pgfpointanchor{#2}{#1}%
    \pgfmathparse{\pgf@y/\pgf@yy}%
    \pgfmathprintnumber{\pgfmathresult}%
}}
\makeatother

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

The source of the difficulty is that ellipses are constructed in a particular way in TikZ. They are paths that start from the x-axis and proceed counter-clockwise around their centre. The vast majority of the time, the exact parametrisation doesn't matter. You appear to have found the one situation where it does!

In the actual question, you only want to be able to mirror the ellipse, and so draw it starting from the negative x-axis (the title of the question suggests a more flexible approach). That's actually not too hard since we can exploit the symmetry of the ellipse. The key is to provide it with a negative x-radius, since then it will start from the negative x-axis (and proceed clockwise, but we could correct for that by negating the y-radius as well). To do this, we interrupt the call from the node shape to the drawing command and flip the sign of the x-radius. The simplest way to do this is to redefine the \pgfpathellipse macro to do the negation and then call the original macro. The following code does this.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations,shapes,decorations.markings}
\makeatletter
\let\origpgfpathellipse=\pgfpathellipse
\def\revpgfpathellipse#1#2#3{%
  #2%
  \pgf@xa=-\pgf@x
  \origpgfpathellipse{#1}{\pgfqpoint{\pgf@xa}{0pt}}{#3}}
\makeatother

\tikzset{
  reversed ellipse/.style={
    ellipse,
    reverse the ellipse%
  },
  reverse the ellipse/.code={
    \let\pgfpathellipse=\revpgfpathellipse
  }
}
\begin{document}
\begin{tikzpicture}
\node[ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,0) {hello world};

\node[reversed ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,-2) {hello world};
\end{tikzpicture}

\end{document}

Here's the result:

rotated ellipse

(the arrow got clipped, but you can see where it lies)

Best Answer

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[Tex/LaTex] Accessing the logic values of a TikZ coordinate

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

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