Bsrgvty

Could someone, whenever it's possible, post a minimal tikZ example to draw this? I also would like to put an "R" inside the upper box. This is mi code so far (I know, it's a mess):

documentclass[tikz]standalone
begindocument
tikzstylevspecies=[rectangle, minimum size=0.5cm,draw=black,fill=blue]
begintikzpicture

node [vspecies] (I) I ;
node [vspecies, above left of = I] (N) M ;
node [vspecies, below left of = I] (K) K ;
draw [->,thick] (S.south east) -- node small$N$ (M) ; ;
draw [->,thick] (C) -- node [below right] small$M$ (M) ;

endtikzpicture
enddocument

Just for fun.

documentclass[tikz]standalone
usetikzlibrarypositioning
begindocument
tikzsetvspecies/.style=rectangle, minimum size=0.5cm,draw=blue
begintikzpicture[>=latex]
 node[draw,minimum width=1cm,minimum height=2cm,
 label=left:$M$,label=above:$N$] (R)$R$;
 node [vspecies,below left=1cm and 0.2cm of R,minimum height=1.2cm,
 label=left:$M$,label=above:$K$] (R1) ;
 node [vspecies,below right=1cm and 0.2cm of R,minimum width=1.2cm,
 label=left:$K$,label=above:$N$] (R2) ;
 draw [->,thick,shorten >=1mm,shorten <=1mm] (R.south west) -- (R1.north east);
 draw [->,thick,shorten >=1mm,shorten <=1mm] (R.south east) -- (R2.north west);
endtikzpicture
enddocument

Something like this?

documentclass[tikz,margin=1mm]standalone
usetikzlibrarypositioning
begindocument
begintikzpicture
beginscope[local bounding box=a]
 node[minimum width=2cm,minimum height=3cm,draw] (main-a) ;
 path (main-a.west) node[left] $N$ (main-a.north) node[above] $M$;
endscope
beginscope[local bounding box=b2]
 node[minimum width=2cm,minimum height=1cm,draw,below right=of main-a] (main-b2) ;
 path (main-b2.east) node[right] $K$ (main-b2.north) node[above] $M$;
endscope
beginscope[local bounding box=b1]
 node[minimum width=1cm,minimum height=3cm,draw,below left=of main-a] (main-b1) ;
 path (main-b1.west) node[left] $N$ (main-b1.north) node[above] $K$;
endscope
draw[-stealth] (main-a.south) -- (b1.north east);
draw[-stealth] (main-a.south) -- (b2.north west);
endtikzpicture
enddocument

Here is an overkill solution that defines a new pics "shape" (see section 18.2 of the 3.1.1 tikz manual),together with some custom pgfkeys for styling it. The end result is that you can produce:

using code:

documentclass[tikz, border=5mm]standalone
usetikzlibrarypositioning

begindocument
pgfkeys/vspecies/.is family, /vspecies,
 colour/.initial = black, % rectangle colour
 fill/.initial = white, % default fill
 top label/.initial = M, % label on right
 right label/.initial= N, % label on left
 bottom label/.initial=, % label on left
 left label/.initial=, % label on left
 X/.initial = 5mm, % default width
 Y/.initial = 5mm, % default height
 shape/.initial = rectangle % default shape


tikzset
pics/vspecies/.style args=#1,#2% node name, pgfkeys key-value pairs
 code = 
 pgfkeys/vspecies, #2
 node[pgfkeysvalueof/vspecies/shape,
 minimum size=pgfkeysvalueof/vspecies/X,
 minimum height=pgfkeysvalueof/vspecies/Y,
 draw=pgfkeysvalueof/vspecies/colour,
 fill=pgfkeysvalueof/vspecies/fill,
 label=east:pgfkeysvalueof/vspecies/left label,
 label=north:pgfkeysvalueof/vspecies/top label,
 label=south:pgfkeysvalueof/vspecies/bottom label,
 label=west:pgfkeysvalueof/vspecies/right label,
 ](#1) at (0,0);
 
 


begintikzpicture
 pic at (0,0) vspecies=A,colour=red,Y=10mm;
 pic[below left=10mm of A] vspecies=B,top label=K,colour=blue,Y=20mm;
 pic[below right=10mm of A] vspecies=C,fill=blue!10,X=10mm,shape=circle,left label=N,right label=;
 draw[->](A.south west)--(B.north east);
 draw[->](A.south east)--(C.north west);
endtikzpicture

enddocument

The vspecies pic command take two arguments: the first is the name of a (normal) tikz node label and the second argunment is a comma separated list of key-value pairs tha specify:

• the colour of the rectangle (default black)


• the fill colour (default white)


• the top label (default M)


• the left label (default "")


• the bottom label (default "")


• the left label (default N)


• the minimum X width


• the minimum Y height


• the shape (default rectangle)

As I said, this is overkill (and I was bored:)

Final version:

documentclass[tikz,margin=1mm]standalone
usetikzlibrarypositioning
begindocument
sffamily
begintikzpicture
beginscope[local bounding box=a]
node[minimum width=2cm,line width=0.199mm,minimum height=3cm,draw=black] (main-a) R;
path (main-a.west) node[left] N (main-a.north) node[above] M;
endscope
beginscope[local bounding box=b2]
node[minimum width=2cm,line width=0.199mm,minimum height=1cm,draw=blue,below right=of main-a] (main-b2) ;
path (main-b2.east) node[right] K (main-b2.north) node[above] M;
endscope
beginscope[local bounding box=b1]
node[minimum width=1cm,line width=0.199mm,minimum height=3cm,draw=blue,below left=of main-a] (main-b1) ;
path (main-b1.west) node[left] N (main-b1.north) node[above] K;
endscope
draw[-stealth] (main-a.south) -- (b1.north east);
draw[-stealth] (main-a.south) -- (b2.north west);
endtikzpicture
enddocument