I'm attempting to draw a hierarchical diagram. I already found this example and a corresponding question. This helps a lot but unfortunately I need a slightly more sophisticated diagram and don't know how to achieve my goals.
My code looks as follows:
% Hierarchical diagram
% Author: cfr
\documentclass[tikz,border=10pt]{standalone}
\usepackage{forest}
\usetikzlibrary{arrows.meta, shapes.geometric, calc, shadows}
\colorlet{mygreen}{green!75!black}
\colorlet{col1in}{red!30}
\colorlet{col1out}{red!40}
\colorlet{col2in}{mygreen!40}
\colorlet{col2out}{mygreen!50}
\colorlet{col3in}{blue!30}
\colorlet{col3out}{blue!40}
\colorlet{col4in}{mygreen!20}
\colorlet{col4out}{mygreen!30}
\colorlet{col5in}{blue!10}
\colorlet{col5out}{blue!20}
\colorlet{col6in}{blue!20}
\colorlet{col6out}{blue!30}
\colorlet{col7out}{orange}
\colorlet{col7in}{orange!50}
\colorlet{col8out}{orange!40}
\colorlet{col8in}{orange!20}
\colorlet{linecol}{blue!60}
\begin{document}
\pgfkeys{/forest,
rect/.append style = {rectangle, rounded corners = 2pt,
inner color = col6in, outer color = col6out},
ellip/.append style = {ellipse, inner color = col5in,
outer color = col5out},
orect/.append style = {rect, font = \sffamily\bfseries\LARGE,
text width = 325pt, text centered,
minimum height = 10pt, outer color = col7out,
inner color=col7in},
oellip/.append style = {ellip, inner color = col8in, outer color = col8out,
font = \sffamily\bfseries\large, text centered}}
\begin{forest}
for tree={
font=\sffamily\bfseries,
line width=1pt,
draw=linecol,
ellip,
align=center,
child anchor=north,
parent anchor=south,
drop shadow,
l sep+=12.5pt,
edge path={
\noexpand\path[color=linecol, rounded corners=5pt,
>={Stealth[length=10pt]}, line width=1pt, ->, \forestoption{edge}]
(!u.parent anchor) -- +(0,-5pt) -|
(.child anchor)\forestoption{edge label};
},
where level={3}{tier=tier3}{},
where level={0}{l sep-=15pt}{},
where level={1}{
if n={1}{
edge path={
\noexpand\path[color=linecol, rounded corners=5pt,
>={Stealth[length=10pt]}, line width=1pt, ->,
\forestoption{edge}]
(!u.west) -| (.child anchor)\forestoption{edge label};
},
}{
edge path={
\noexpand\path[color=linecol, rounded corners=5pt,
>={Stealth[length=10pt]}, line width=1pt, ->,
\forestoption{edge}]
(!u.east) -| (.child anchor)\forestoption{edge label};
},
}
}{},
}
[Title, inner color=col1in, outer color=col1out
[X, inner color=col2in, outer color=col2out
[X1, inner color=col4in, outer color=col4out
[X11, rect, name=X11
]
[X12, rect, name=X12
]
[X13, rect, name=X13
]
[X14, rect, name=X14
]
[X15, rect, name=X15
]
[X16, rect, name=X16
]
[X17, rect, name=X17
]
[X18, rect, name=X18
]
]
[X2, inner color=col4in, outer color=col4out
]
[X3, inner color=col4in, outer color=col4out
]
]
[Y, inner color=col3in, outer color=col3out
[Convex Relaxation
[Sparse Signal\\Estimate, rect, name=sse1
]
]
[Greedy Pursuits
[Sparse Signal\\Estimate, rect, name=sse2
]
]
[, phantom, calign with current
[A\\B, phantom
[Our Work, orect, name=us
[{Improved Sparse Signal Estimate!}, oellip
]
]
]
]
[Non-Convex\\Minimisation Methods
[Sparse Signal\\Estimate, rect, name=sse3
]
]
[Combinatorial\\Algorithms
[Sparse Signal\\Estimate, rect, name=sse4
]
]
]
]
\begin{scope}[color = linecol, rounded corners = 5pt,
>={Stealth[length=10pt]}, line width=1pt, ->]
\draw (sse2.south) -- (us.north -| sse2.south);
\draw (sse3.south) -- (us.north -| sse3.south);
\coordinate (c1) at ($(sse1.south)!2/5!(sse2.south)$);
\coordinate (c2) at ($(sse3.south)!2/5!(sse4.south)$);
\draw (sse1.south) -- +(0,-10pt) -| (us.north -| c1);
\draw (sse4.south) -- +(0,-10pt) -| (us.north -| c2);
\end{scope}
\end{forest}
\end{document}
The results can be seen below:
What I would like to have are arrows between the nodes X1, X2 and X3 and the nodes X11-X18 in order to avoid having to concatenate nodes X11-X18 three times (once for each higher level node). In short, I'm looking for a way to draw the red arrows in the diagram below:
