Fraction ticks on a pgfplot

Question

I'm trying to use pgfplots to produce a plot with fractional ticks on the y-axis. Unfortunately pgfplots doesn't deal very nicely with things like yticks = {1/36, 1/18, 1/12, 1/9, 5/36, 1/6}, and gives various errors about how to represent them.

In the end, I got fed up and scaled my plot so that it passes through integer points instead. However, I'd still like to have the fractional ticks in their lowest form, because currently I have Here is my code:

\documentclass{article}
\usepackage{pgfplots}

\begin{document}
   \pgfplotsset{
      standard/.style={
         axis x line=middle,
         axis y line=middle,
         enlarge x limits=0.15,
         enlarge y limits=0.15,
         every axis x label/.style={at={(1,0.1)},anchor=north west},
         every axis y label/.style={at={(0.1,1.1)},anchor=north},
         every axis plot post/.style={mark options={fill=white}}
      }
   }
   \begin{tikzpicture}
      \begin{axis}[
      standard,
      domain = 2:12,
      samples = 11,
      xlabel={$x$},
      ylabel={$\Pr(X=x)$},
      ymin=0,
      yticklabel={$\frac{\pgfmathprintnumber{\tick}}{36}$},
      ytick = {1, 2, 3, 4, 5, 6},
      ymax=6]
      \addplot+[ycomb,black,thick] {(6-abs(x-7))};
      \end{axis}
   \end{tikzpicture}
\end{document}

Is there a better way to go about the whole thing? I appreciate any help.

Answer 1

There are two possible options to achieve this:

1. Just need to write yticklabels={$1/36$, $1/18$, $1/12$, $1/9$, $5/36$, $1/6$} for simplified fractions (or yticklabels={$1/36$, $2/36$, $3/36$, $4/36$, $5/36$, $6/36$}, if you will), or with common fraction displaying by using yticklabels={$\frac{1}{36}$, $\frac{1}{18}$, $\frac{1}{12}$, $\frac{1}{9}$, $\frac{5}{36}$, $\frac{1}{6}$}. Or
2. write yticklabel={$\pgfmathprintnumber{\tick}/{36}$} instead of yticklabel={$\frac{\pgfmathprintnumber{\tick}}{36}$}.

Note, the difference between them is that with the first one, you write yticklabels=... and mention labels one by one at will (simplified or non simplified), and with the second one, you write yticklabel=... with the automatic generating code (but will display non simplified fractions).

Simplified fractions

Common fraction displaying

Non simplified fractions

Also, to place the ylabel above the vertical line and centered, you can put

every axis y label/.style={at={(current axis.above origin)},anchor=south},

---

And just to let you know, it is important to include the line

\pgfplotsset{compat=1.15}

in preamble when using PGFPlots. See this answer for further information.

Answer 2

Here is another way, making use of gcd.

\documentclass{article}
\usepackage{pgfplots}
\newcommand{\Fraction}[2]{%
\pgfmathtruncatemacro{\tmpNumerator}{#1/gcd(#1,#2)}
\pgfmathtruncatemacro{\tmpDenominator}{#2/gcd(#1,#2)}
\ensuremath{\frac{\tmpNumerator}{\tmpDenominator}}
}
\begin{document}
   \pgfplotsset{
      standard/.style={
         axis x line=middle,
         axis y line=middle,
         enlarge x limits=0.15,
         enlarge y limits=0.15,
         every axis x label/.style={at={(1,0.1)},anchor=north west},
         every axis y label/.style={at={(0.1,1.1)},anchor=north},
         every axis plot post/.style={mark options={fill=white}}
      }
   }
   \begin{tikzpicture}
      \begin{axis}[
      standard,
      domain = 2:12,
      samples = 11,
      xlabel={$x$},
      ylabel={$\Pr(X=x)$},
      ymin=0,
      yticklabel={$\Fraction{\tick}{36}$},
      ytick = {1, 2, 3, 4, 5, 6},
      ymax=6]
      \addplot+[ycomb,black,thick] {(6-abs(x-7))};
      \end{axis}
   \end{tikzpicture}
\end{document}