heatmap.tex

\documentclass[margin=10pt]{standalone}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
%
\usetikzlibrary{shapes, shapes.geometric, shapes.arrows, arrows, patterns, positioning, calc}
%
\begin{document}
\begin{tikzpicture}[scale=0.6]
    \foreach \y [count=\n] in {
        {74,25,39,20,3,3,3,3,3},
        {25,53,31,17,7,7,2,3,2},
        {39,31,37,24,3,3,3,3,3},
        {20,17,24,37,2,2,6,5,5},
        {3,7,3,2,12,1,0,0,0},
        {3,7,3,2,1,36,0,0,0},
        {3,2,3,6,0,0,45,1,1},
        {3,3,3,5,0,0,1,23,1},
        {3,2,3,5,0,0,1,1,78},
      } {
        % column labels
        \ifnum\n<10
          \node[minimum size=6mm] at (\n, 0) {\n};
        \fi
        % heatmap tiles
        \foreach \x [count=\m] in \y {
          \node[line width=1.2mm, draw=white, fill=yellow!\x!purple, minimum size=6mm, text=white] at (\m,-\n) {\x};
        }
      }
  
    % row labels
    \foreach \a [count=\i] in {a,b,c,d,e,f,g,h,i} {
      \node[minimum size=6mm] at (0,-\i) {\a};
    }
  \end{tikzpicture}
\end{document}