Mfcttrf

In this figure,

documentclass[border=1mm]standalone
usepackageamsmath
usepackagetikz,pgfplots
pgfplotssetwidth=11cm,compat=1.15
usetikzlibrarypositioning %<<<<----OJO
usetikzlibraryarrows.meta,calc,decorations.markings,math,arrows.meta

begindocument

begintikzpicture[
roundnode/.style=circle, draw=black!60, fill=green!5, minimum size=8.5mm, line width=1.5mm,
squarednode/.style=rectangle, draw=red!60, fill=red!5, minimum size=7mm,
align=center,node distance=2.25cm,
scale=4,
% every node/.style=scale=4,
every node/.style=transform shape
]
%Nodes
node[roundnode] (A) Large 1;
node[roundnode] (B) [below of =A] Large 2;
node[roundnode] (C) [below of= B] Large 3;
node[roundnode] (D) [below of= C] Large 4;
node[roundnode, node distance=2.75cm,] (M) [below of= D] Large $m$;
%%%

%% CARTS
node[squarednode] (C1) [right of= A] Large c1;
node[squarednode, node distance=1.25cm,] (C2) [right of= C1] Large c2;
node[squarednode, node distance=1.25cm,] (C3) [right of= C2] Large c3;
%
node[squarednode] (C4) [right of= B] Large c4; 
%
node[squarednode] (C5) [right of= C] Large c5; 
node[squarednode, node distance=1.25cm,] (C6) [right of= C5] Large c6;
%
node[squarednode] (C7) [right of= D] Large c7;
node[squarednode, node distance=1.25cm,] (C8) [right of= C7] Large c8;
node[squarednode, node distance=1.25cm,] (C9) [right of= C8] Large c9;
%
node[squarednode] (C10) [right of= M] Large c10; 

%%
node[circle, minimum size=0.5mm, fill=black!40, node distance=5cm, yshift=-0.25cm, inner sep=0pt] (E0) [right of= C6] ;



%Lines
draw[-,line width=0.5mm,] (A) -- (B);
draw[-,line width=0.5mm] (B) -- (C);
draw[-,line width=0.5mm,] (C) -- (D);
%
draw[loosely dotted,line width=0.65mm] (D) -- (M);

draw [dashed,black,line width=0.5mm,] (A.west) to [out=210,in=140] (C.west);
draw [dashed,black,line width=0.5mm,] (B.west) to [out=210,in=140] (D.west);

%%%%%%%%%%%%%
% From X to carts
draw [->[scale=1.5], red,line width=0.5mm,] (E0.north) to [out=90,in=0] (C3.east);
draw [->[scale=1.5], red,line width=0.5mm,] (E0.north) to [out=120,in=0] (C4.east);
draw [->[scale=1.5], red,line width=0.5mm,] (E0.west) to [out=165,in=0] (C6.east);
draw [->[scale=1.5], red,line width=0.5mm,] (E0.south) to [out=235,in=0] (C9.east);
draw [->[scale=1.5], red,line width=0.5mm,] (E0.south) to [out=270,in=0] (C10.east);

%%%%
%% MORE CARTS
node[squarednode, node distance=0.75cm, outer sep = 0.20cm] (E1) [right of= E0] Large c11;
node[squarednode, node distance=1.50cm, outer sep = 0.20cm] (E2) [right of= E1] Large c12;
node[squarednode, node distance=2.00cm, outer sep = 0.20cm] (E3) [right of= E2] Large c13;

%% lines dotted
draw[-, red, loosely dotted, line width=0.65mm,] (E1) -- (E2);
draw[-, red, loosely dotted, line width=0.65mm,] (E2) -- (E3);
%
node[yshift=-1.25cm, xshift= 0.25cm] (T1) [above of =E2] $lambda$ arrivals per second;

%%%%%
% LEGEND
node[squarednode, yshift=-1cm, xshift=-0.5cm] (L11) [below of= E2] C;
node[yshift=1.25cm,] (L12) [below of= L11] Shopping\Cart;
%
node[roundnode, ] (L21) [right of= L11] ;
node[yshift=1.25cm,] (L22) [below of= L21] Shop\Paypoint;

endtikzpicture 

enddocument

I would like to replace each of the red square nodes by a shopping cart tikzpicture (no text is needed inside the cart):

documentclass[border=1mm]standalone
usepackageamsmath
usepackagepgf,tikz,pgfplots
pgfplotssetcompat=1.15
usetikzlibraryarrows

begindocument
 % definecolorzzttqqrgb0.6,0.2,0
% definecolorududffrgb0.3,0.3,1

 begintikzpicture[line cap=round,line join=round,>=triangle 45]
 % draw[help lines,step=] (-3,-1) grid (3,7);
 filldraw[line width=2pt,color=purple,fill=brown!30] 
 (-2.58,4.28) -- (-2.30,2.93) -- (0.59,2.67) -- (1.11,4.39) -- cycle;
 draw [line width=2pt] (-2.40,2.16)-- (0.84,2.16);
 draw [line width=2pt] (0.84,2.16)-- (0.59,2.67);
 draw [line width=2pt] (1.11,4.39)-- (1.39,4.78);
 draw [line width=2pt] (1.39,4.78)-- (1.72,4.78);
 draw [line width=2.8pt] (-2.17,1.78) circle (0.25cm);
 draw [line width=2.8pt] (0.43,1.78) circle (0.25cm);
 endtikzpicture

enddocument

with the cart scaled to similar size of the square red nodes.

How can I replace the square nodes by carts? (e.g. c1, c2 and c3 will be three carts at the right of node 1).

There are 2.5 methods to make a TikZ picture a node:

1. Use path picture.


2. Use a savebox.


3. Use pics. This is strictly speaking not a node, hence "2.5" instead of 3 possibilities.

Let's focus on option 2. Your cart gets stored in a savebox. It can be the content of the nodes, or you can make it a style using node contents. (In this case you need to be a bit more carful with the syntax, node (C1) [cart]; works but node[cart] (C1); doesn't.) Then there are several off-topic comments:

• You were loading packages and libraries that you didn't use. I got rid of them.


• You were loading positioning but not using it. Instead of right of=A use the positioning syntax right=of A or right=<distance> of A. This makes it much easier to arrange the nodes.


• If you repeatedly use the same styles it is more convenient to use scopes.

All this is to some extent done in the following MWE (which is not fully optimized, though):

documentclass[border=1mm]standalone
usepackageamsmath
usepackagetikz
usetikzlibrarypositioning,arrows.meta
newsaveboxChart
sboxChartbegintikzpicture[line cap=round,line join=round,scale=0.25]
 % draw[help lines,step=] (-3,-1) grid (3,7);
 pgfgettransformentriesmyatmptmptmptmptmp
 filldraw[line width=mya*2pt,color=purple,fill=brown!30] 
 (-2.58,4.28) -- (-2.30,2.93) -- (0.59,2.67) -- (1.11,4.39) -- cycle;
 draw [line width=mya*2pt] (-2.40,2.16)-- (0.84,2.16);
 draw [line width=mya*2pt] (0.84,2.16)-- (0.59,2.67);
 draw [line width=mya*2pt] (1.11,4.39)-- (1.39,4.78);
 draw [line width=mya*2pt] (1.39,4.78)-- (1.72,4.78);
 draw [line width=mya*2.8pt] (-2.17,1.78) circle (0.25cm);
 draw [line width=mya*2.8pt] (0.43,1.78) circle (0.25cm);
 endtikzpicture
begindocument

begintikzpicture[>=Stealth,
roundnode/.style=circle, draw=black!60, fill=green!5, minimum size=8.5mm, line width=1.5mm,
squarednode/.style=rectangle, draw=red!60, fill=red!5, minimum size=7mm,
align=center,node distance=2.25cm,
scale=4,
% every node/.style=scale=4,
every node/.style=transform shape,
cart/.style=node contents=useboxChart
]
 %Nodes
 node[roundnode] (A) Large 1;
 node[roundnode] (B) [below of =A] Large 2;
 node[roundnode] (C) [below=of B] Large 3;
 node[roundnode] (D) [below=of C] Large 4;
 node[roundnode, node distance=2.75cm,] (M) [below=of D] Large $m$;
 %%%

 %% CARTS
 beginscope[node distance=3mm,nodes=cart]
 node (C1) [right=of A];
 node (C2) [right=of C1];
 node (C3) [right=of C2];
 %
 node (C4) [right=of B]; 
 %
 node (C5) [right=of C]; 
 node (C6) [right=of C5];
 %
 node (C7) [right=of D];
 node (C8) [right=of C7];
 node (C9) [right=of C8];
 %
 node (C10) [right=of M]; 
 endscope
 %%
 node[circle, minimum size=0.5mm, fill=black!40, node distance=5cm, yshift=-0.25cm, inner sep=0pt] (E0) [right=of C6] ;



 %Lines
 draw[-,line width=0.5mm,] (A) -- (B);
 draw[-,line width=0.5mm] (B) -- (C);
 draw[-,line width=0.5mm,] (C) -- (D);
 %
 draw[loosely dotted,line width=0.65mm] (D) -- (M);

 draw [dashed,black,line width=0.5mm,] (A.west) to [out=210,in=140] (C.west);
 draw [dashed,black,line width=0.5mm,] (B.west) to [out=210,in=140] (D.west);

 %%%%%%%%%%%%%
 % From X to carts
 draw [->[scale=1.5], red,line width=0.5mm,] (E0.north) to [out=90,in=0] (C3.east);
 draw [->[scale=1.5], red,line width=0.5mm,] (E0.north) to [out=120,in=0] (C4.east);
 draw [->[scale=1.5], red,line width=0.5mm,] (E0.west) to [out=165,in=0] (C6.east);
 draw [->[scale=1.5], red,line width=0.5mm,] (E0.south) to [out=235,in=0] (C9.east);
 draw [->[scale=1.5], red,line width=0.5mm,] (E0.south) to [out=270,in=0] (C10.east);

 %%%%
 %% MORE CARTS
 beginscope[nodes=cart]
 node (E1) [right=3mm of E0];
 node (E2) [right=2mm of E1];
 node (E3) [right=5mm of E2];
 endscope
 %% lines dotted
 draw[-, red, loosely dotted, line width=0.65mm,] (E1) -- (E2);
 draw[-, red, loosely dotted, line width=0.65mm,] (E2) -- (E3);
 %
 node[yshift=-1.25cm, xshift= 0.25cm] (T1) [above=of E2] $lambda$ arrivals per second;

 %%%%%
 % LEGEND
 node (L11) [below left=1cm and 1mm of E2,cart];
 node[yshift=1.25cm,] (L12) [below=of L11] Shopping\Cart;
 %
 node[roundnode, ] (L21) [right=of L11] ;
 node[yshift=1.25cm,] (L22) [below=of L21] Shop\Paypoint;

endtikzpicture 
enddocument