Nehtdx

I am drawing a matrix using tikz-cd. I would like to draw some vertical and horizontal lines on it too to indicate particular submatrices but I don't understand the syntax. This is my M(N)WE:

documentclassarticle
usepackage[margin=1cm]geometry
usepackagetikz-cd
begindocument
begintikzcd[column sep=3pt, row sep=5pt,nodes=inner sep=0pt,align=center,
text width=width("20")]
&&0&0&0&0&0&0&0&0&0&0\
&0&1&2&3&4&5&6&7&8&9&10\
0&1&0&1&2&3&4&5&6&7&8&9\
0&2&1&0&1&2&3&4&5&6&7&8\
0&3&2&1&0&1&2&3&4&5&6&7\
0&4&3&2&1&0&1&2&3&4&5&6
foreach x in 1,3

 draw 
 ([yshift=-3,xshift=-.125pgflinewidth]mat-x-1.south west) -- 
 ([yshift=-3,xshift=-.125pgflinewidth]mat-x-12.south east);

foreach y in 2

 draw 
 ([yshift=.5pgflinewidth]mat-1-y.north east) -- 
 ([yshift=.5pgflinewidth]mat-14-y.south east);

endtikzcd

enddocument

This is syntactically incorrect but works if you remove the foreach loops. How can I use the foreach...draw commands with a tikz-cd drawn matrix?

Are you looking for this?

documentclassarticle
usepackage[margin=1cm]geometry
usepackagetikz-cd
begindocument
begintikzcd[column sep=3pt, row sep=5pt,nodes=inner sep=0pt,align=center,
text width=width("20"),nodes in empty cells,
execute at end picture=
foreach x in 1,3

 draw 
 ([yshift=-3,xshift=-.125pgflinewidth]tikzcdmatrixname-x-1.south west) -- 
 ([yshift=-3,xshift=-.125pgflinewidth]tikzcdmatrixname-x-12.south east);

foreach y in 3

 draw 
 ([yshift=.5pgflinewidth]tikzcdmatrixname-1-y.north west) -- 
 ([yshift=.5pgflinewidth]tikzcdmatrixname-6-y.south west);
]
&&0&0&0&0&0&0&0&0&0&0\
&0&1&2&3&4&5&6&7&8&9&10\
0&1&0&1&2&3&4&5&6&7&8&9\
0&2&1&0&1&2&3&4&5&6&7&8\
0&3&2&1&0&1&2&3&4&5&6&7\
0&4&3&2&1&0&1&2&3&4&5&6
endtikzcd
enddocument

Here I was employing Henri Menke's nice answer and added nodes in empty cells and changed some numbers to only use existing nodes.

ADDENDUM: If you want to the lines right in the middle between the cells without having to add all the shifts by fractions of the line width, you could use the calc library.

documentclassarticle
usepackage[margin=1cm]geometry
usepackagetikz-cd
usetikzlibrarycalc
begindocument
begintikzcd[column sep=3pt, row sep=5pt,nodes=inner sep=0pt,align=center,
text width=width("20"),nodes in empty cells,
execute at end picture=
foreach x [evaluate=x as xp using int(x+1)] in 1,3

 draw ($(tikzcdmatrixname-x-2.south)!0.5!(tikzcdmatrixname-xp-2.north)$)
 coordinate (aux)
 ([xshift=-.1em]tikzcdmatrixname.west
foreach y [evaluate=y as ym using int(y-1)] in 3
aux);
]
&&0&0&0&0&0&0&0&0&0&0\
&0&1&2&3&4&5&6&7&8&9&10\
0&1&0&1&2&3&4&5&6&7&8&9\
0&2&1&0&1&2&3&4&5&6&7&8\
0&3&2&1&0&1&2&3&4&5&6&7\
0&4&3&2&1&0&1&2&3&4&5&6
endtikzcd
enddocument

As for the question what this might be good for: there are certain things that are somewhat harder to achieve with a table like e.g.

documentclassarticle
usepackage[margin=1cm]geometry
usepackagetikz-cd
usetikzlibrarycalc,through,backgrounds 
tikzsetcircle through 3 points/.style n args=3% 
insert path=let p1=($(#1)!0.5!(#2)$), 
p2=($(#1)!0.5!(#3)$), 
p3=($(#1)!0.5!(#2)!1!-90:(#2)$), 
p4=($(#1)!0.5!(#3)!1!90:(#3)$), 
p5=(intersection of p1--p3 and p2--p4) 
in , 
at=(p5), 
circle through= (#1) 
 
begindocument
begintikzcd[column sep=3pt, row sep=5pt,nodes=inner sep=0pt,align=center,
text width=width("20"),nodes in empty cells,
execute at end picture=
foreach x [evaluate=x as xp using int(x+1)] in 1,3

 draw ($(tikzcdmatrixname-x-2.south)!0.5!(tikzcdmatrixname-xp-2.north)$)
 coordinate (aux)
 ([xshift=-.1em]tikzcdmatrixname.west
foreach y [evaluate=y as ym using int(y-1)] in 3
aux);

beginscope[on background layer]
 node[circle through 3
 points=tikzcdmatrixname-2-2tikzcdmatrixname-3-1tikzcdmatrixname-3-3,
 fill=blue!20]; 
endscope
]
&&0&0&0&0&0&0&0&0&0&0\
&0&1&2&3&4&5&6&7&8&9&10\
0&1&0&1&2&3&4&5&6&7&8&9\
0&2&1&0&1&2&3&4&5&6&7&8\
0&3&2&1&0&1&2&3&4&5&6&7\
0&4&3&2&1&0&1&2&3&4&5&6
endtikzcd
enddocument

Yet for many purposes, the table approach suggested by Joule V is just fine or even better. It really depends on what you want to do in the end.

Just for fun: if you want to make that matrix, why don't use a table? The code is much shorter:

documentclassarticle
begindocument
renewcommandarraystretch1.3
begintabularcc
 &&0&0&0&0&0&0&0&0&0&0\hline
 &0&1&2&3&4&5&6&7&8&9&10\
 0&1&0&1&2&3&4&5&6&7&8&9\hline
 0&2&1&0&1&2&3&4&5&6&7&8\
 0&3&2&1&0&1&2&3&4&5&6&7\
 0&4&3&2&1&0&1&2&3&4&5&6
endtabular
enddocument

Coloring the text is not difficult, isn't it? If you want to draw some arrows, tikzmark may be an option. Anyway, if I were you, I would use a simple table. :)

Add an arrow

documentclassarticle
usepackagetikz
begindocument
renewcommandarraystretch1.3
begintabularcc
 &&0&0&0&0&0&0&0&0&0&0\hline
 &0&1&2&3&4&5&6&7&8&9&10\
 0&tikz[baseline,remember picture]node[anchor=base,inner sep=0pt] (node1) 1;&0&1&2&3&4&5&6&7&8&9\hline
 0&2&1&0&1&2&3&4&5&6&7&8\
 0&3&2&1&0&1&2&tikz[baseline,remember picture]node[anchor=base,inner sep=0pt] (node2) 3;&4&5&6&7\
 0&4&3&2&1&0&1&2&3&4&5&6
endtabular

begintikzpicture[remember picture,overlay]
draw[red,very thick,-latex] (node1) -- (node2);
endtikzpicture
enddocument

Color row(s)

documentclassarticle
usepackagetikz
usepackagexcolor,colortbl
begindocument
renewcommandarraystretch1.3
begintabularcc
 rowcolorred!20&&0&0&0&0&0&0&0&0&0&0\hline
 rowcolorred!20&0&1&2&3&4&5&6&7&8&9&10\
 0&1&0&1&2&3&4&5&6&7&8&9\hline
 0&2&1&0&1&2&3&4&5&6&7&8\
 0&3&2&1&0&1&2&3&4&5&6&7\
 0&4&3&2&1&0&1&2&3&4&5&6
endtabular
enddocument

Color column(s)

documentclassarticle
usepackagetikz
usepackagexcolor,colortbl
begindocument
renewcommandarraystretch1.3
begintabularccc>columncoloryellow!50cc>columncolorgreen!20ccccc
 &&0&0&0&0&0&0&0&0&0&0\hline
 &0&1&2&3&4&5&6&7&8&9&10\
 0&1&0&1&2&3&4&5&6&7&8&9\hline
 0&2&1&0&1&2&3&4&5&6&7&8\
 0&3&2&1&0&1&2&3&4&5&6&7\
 0&4&3&2&1&0&1&2&3&4&5&6
endtabular
enddocument

It is never impossible to work with tables using table commands :)