Diaa
Following up [this answer](https://topanswers.xyz/tex?q=1563#a1815), I would like to get the desired output with a rule that chooses the plane (top or bottom) the edges/arrows are drawn in such a way that they are drawn in the **top half** if the connections/edges involve the nodes of either the input `R(s)` or the output `Y(s)`. Otherwise, the edges are drawn in the **bottom half**.
Specifically speaking, for the following, the edge between `X3(s)` and `sX1(s)` should accordingly be **automatically** drawn in the bottom half.
```
% define the matrix
\edef\mmat{%
{2,-5,3,2},% <= a missing edge of label "3" should be drawn from X3 to sX1
{-6,-2,2,5},%
{1,-3,-4,7},%
{-4,6,9,0}%
}
\documentclass[tikz,border=5mm]{standalone}
\usetikzlibrary{calc,decorations.markings,positioning,arrows.meta}
\newif\iflabrev
\begin{document}
\begin{tikzpicture}[node distance = 15 mm,
label revd/.is if=labrev,
label revd/.default=true,
amark/.style = {
decoration={
markings,
mark=at position {0.5} with {
\arrow{stealth},
\iflabrev \node[below] {#1};\else \node[above] {#1};\fi
}
},
postaction={decorate}
}, % make the mark an entry of the \mmat matrix
pmark/.code n args={2}{%
\pgfmathtruncatemacro{\myi}{int({\mmat}[\numexpr#1][\numexpr#2])}%
\tikzset{suppress if 0=\myi,
amark={$\myi$}}% <- changed
},
terminal/.style 2 args={draw,alias=ln,circle,inner sep=2pt,label={#1:#2}},
% semicircle path
semicircle/.style={to path={let \p1=($(\tikztotarget)-(\tikztostart)$)
in \ifdim\x1>0pt
(\tikztostart.north) arc[start angle=180,end angle=0,radius=0.5*\x1]
\else
(\tikztostart.south) arc[start angle=0,end angle=-180,radius=-0.5*\x1]
\fi}},
add key if/.code n args={3}{\pgfmathtruncatemacro{\itest}{(#1?0:1)}%
\ifcase\itest
\tikzset{#2}%
\else
\tikzset{#3}%
\fi
},suppress if 0/.style={add key if={#1==0}{opacity=0}{}},
switch if/.style 2 args={}
]
\pgfmathtruncatemacro{\dimy}{dim({\mmat})} % number of rows
\pgfmathtruncatemacro{\dimx}{dim({\mmat}[0])} % number of columns
% create the graph
\path % R node
node[terminal={left}{$R(S)$},alias={X-\dimy}] (R) {}
% loop over matrix entries
foreach \Y [evaluate=\Y as \X using {int(\dimy-\Y)}]
in {1,...,\numexpr\dimy-1}
{node[right=of ln,terminal={below right}{% sX_i node
$sX_{\X}(s)$}](sX-\X){}
node[right=of ln,terminal={below right}{% X_i node
$X_{\X}(s)$}](X-\X){}
% ege from sX_i to X_i
(sX-\X) edge[amark={$\frac{1}{s}$}] (X-\X)
% edge from X_{i+1} to X_i (R had an alias)
(X-\the\numexpr\X+1) edge[pmark={\X-1}{\X},swap] (sX-\X)
% semicircle edge from X_i to sX_i
(X-\X) edge[semicircle,label revd,pmark={\X-1}{\X-1}] (sX-\X)
}
node[right=of ln,terminal={right}{$Y(s)$},alias=sX-\dimy](Y){}
(X-1) edge[pmark={\dimy-1}{0}] (Y)
% we are now done with the horizontal part,
% and have also dealt with the entries on the diagonal and
% the {i-1},i entries
% now we deal with the matrix entries
foreach \X in {1,...,\the\numexpr\dimx-1}
{ foreach \Y in {\the\numexpr\X+1,...,\dimy}
{
\unless\ifnum\X\Y=1\dimy
(X-\X) edge[semicircle,pmark={\Y-1}{\X-1},add key if={\Y==\dimy}{}{label revd}] (sX-\Y)
\fi
\unless\ifnum\numexpr\Y-\X=\numexpr1\relax
(X-\Y) edge[semicircle,pmark={\X-1}{\Y-1}] (sX-\X)
\fi
}};
\end{tikzpicture}
\end{document}
```