matrix image in Beamer

Question

I am preparing a Beamer presentation, and would like to have kind of a function (I will do this several times with different inputs) that given a matrix with elements between 0 and 1 (like an output from matlab: X = rand(10,20), shows a color image (like the output of imagesc(X)) with frames around the cells. So, for example if the input is X =[0.72, 0.70, 0.45, 0.58, 0.34, 0.17, 0.39] the output looks like this image

and if it is a matrix, the following image:

What MATLBA does for imagesc(X) is first making a colormap with RGB values, something like

colormap

ans =

     0         0         0
     0         0    0.6250
     0         0    0.6875
     0         0    0.7500
     0         0    0.8125
     0         0    0.8750
     0         0    0.9375
     0         0    1.0000
     0    0.0625    1.0000
     0    0.1250    1.0000
     0    0.1875    1.0000
     0    0.2500    1.0000
     0    0.3125    1.0000
     0    0.3750    1.0000
     0    0.4375    1.0000
     0    0.5000    1.0000
     0    0.5625    1.0000
     0    0.6250    1.0000
     0    0.6875    1.0000
     0    0.7500    1.0000
     0    0.8125    1.0000
     0    0.8750    1.0000
     0    0.9375    1.0000
     0    1.0000    1.0000
0.0625    1.0000    0.9375
0.1250    1.0000    0.8750
0.1875    1.0000    0.8125
0.2500    1.0000    0.7500
0.3125    1.0000    0.6875
0.3750    1.0000    0.6250
0.4375    1.0000    0.5625
0.5000    1.0000    0.5000
0.5625    1.0000    0.4375
0.6250    1.0000    0.3750
0.6875    1.0000    0.3125
0.7500    1.0000    0.2500
0.8125    1.0000    0.1875
0.8750    1.0000    0.1250
0.9375    1.0000    0.0625
1.0000    1.0000         0
1.0000    0.9375         0
1.0000    0.8750         0
1.0000    0.8125         0
1.0000    0.7500         0
1.0000    0.6875         0
1.0000    0.6250         0
1.0000    0.5625         0
1.0000    0.5000         0
1.0000    0.4375         0
1.0000    0.3750         0
1.0000    0.3125         0
1.0000    0.2500         0
1.0000    0.1875         0
1.0000    0.1250         0
1.0000    0.0625         0
1.0000         0         0
0.9375         0         0
0.8750         0         0
0.8125         0         0
0.7500         0         0
0.6875         0         0
0.6250         0         0
0.5625         0         0
0.5000         0         0

Then, based on this map, assign colors to the elements.

I was wondering if this is possible in tikz?

Answer 1

1. Random Colors:

Here is an adaptation of Drawing grids filled with random selected colors and connecting them which alows you to specify the dimensions of the matrix:

2. Colors Specified per Cell:

If you wish to specify the colors for each cell, then you can use the datatool package to read in a CSV file which contains the mapping from a number to a color. This requires that you specify each cell color. Then the input:

\DrawGrid{
    {1,2,3},
    {3,4,5}}
\DrawGrid{
    { 1, 7, 8, 9,12,11,13, 6, 4, 8},
    { 4, 5,12,15,17, 3, 6, 5, 9, 4},
    { 7, 4, 8, 2,12,14, 7, 3, 6, 5},
    { 3,12, 9,11, 4, 7, 9,16,11,10}}
\DrawGrid{
    {1},
    {5},
    {11},
    {13},
    {3}}

yields:

Notes:

• The filecontents package was used to set up a file to read the mapping from index to color for this test case. It is not needed in you actual use case.

---

Code: Random Colors

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{calc}
\pgfmathdeclarerandomlist{MyRandomColors}{%
    {red}%
    {red!25}%
    {magenta}%
    {magenta!25}%
    {olive}%
    {olive!25}%
    {brown}%
    {brown!10}%
    {violet}%
    {violet!25}%
    {gray}%
    {purple}%
    {yellow}%
    {orange}%
    {orange!25}%
    {cyan}%
    {green}%

}%
\newcommand*{\DrawGrid}[2]{%
\begin{tikzpicture}[scale=.7, ultra thick]
    \foreach \y in {1,...,#2} {
        \foreach \x in {1,...,#1} {
            \pgfmathrandomitem{\RandomColor}{MyRandomColors} 
            \draw [fill=\RandomColor, fill opacity=0.4, draw=none, ultra thick] 
                (\x-1,\y-1) rectangle (\x,\y);
        }%
    }%
    \draw (0, 0) grid (#1, #2);
    \draw (0, 0) rectangle (#1, #2);
\end{tikzpicture}
}
\begin{document}
\DrawGrid{4}{1}
\bigskip
\DrawGrid{8}{5}
\bigskip
\DrawGrid{1}{5}
\bigskip
\end{document}

---

Code: Colors Specified per Cell

%%  Mapping from number to color
\begin{filecontents*}{MyColorMap.csv}
    1, red
    2, red!25
    3, magenta
    4, magenta!25
    5, olive
    6, olive!25
    7, brown
    8, brown!10
    9, violet
    10, violet!25
    11, gray
    12, purple
    13, yellow
    14, orange
    15, orange!25
    16, cyan
    17, green    
\end{filecontents*}
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{calc}
\usepackage{datatool}
\AtBeginDocument{%
   \DTLloaddb[noheader,keys={Index,Color}]{ColorDB}{MyColorMap.csv}%
}%
\newcommand{\RowData}{}%
\newcommand{\ColumnData}{}%
\newcommand{\NumberOfRows}{}%
\newcommand{\NumberOfColumns}{}%
\newcommand*{\DrawGrid}[1]{%
\begin{tikzpicture}[scale=.7, ultra thick]
    \edef\ColumnData{#1}
    \foreach [count=\j from 1] \y in \ColumnData {
        \edef\RowData{\y}%
        \xdef\NumberOfColumns{\j}%
        \foreach [count=\i from 1] \x in \RowData {
        \xdef\NumberOfRows{\i}%
            \DTLgetvalue{\MyColor}{ColorDB}{\x}{2}% "2" is the column with the color
            \draw [fill=\MyColor, fill opacity=0.4, draw=none, ultra thick] 
                (\i-1,-\j+1) rectangle (\i,-\j)
                %node [midway] {\x}% <--- Comment this out if don't want number in cell
                ;
        }%
    }%
    \draw (0, -\NumberOfColumns) grid (\NumberOfRows, 0);
    \draw (0, -\NumberOfColumns) rectangle (\NumberOfRows, 0);
\end{tikzpicture}
}
\begin{document}
\DrawGrid{
    {1,2,3},
    {3,4,5}}
\bigskip
\DrawGrid{
    { 1, 7, 8, 9,12,11,13, 6, 4, 8},
    { 4, 5,12,15,17, 3, 6, 5, 9, 4},
    { 7, 4, 8, 2,12,14, 7, 3, 6, 5},
    { 3,12, 9,11, 4, 7, 9,16,11,10}}
\bigskip
\DrawGrid{
    {1},
    {5},
    {11},
    {13},
    {3}}
\end{document}