DiagrammeR - arrow problems - r

Question

I am trying to create a flowchart using this excellent tutorial: https://dannyjnwong.github.io/STROBE-CONSORT-Diagrams-in-R/
library(DiagrammeR)
library(DiagrammeRsvg) #Needed if you want to export the image
library(rsvg) #Needed if you want to export the image
#Set the values which will go into each label.
a1 <- 'Total available patients\n(n = x)'
b1 <- ''
c1 <- ''
d1 <- 'Included for analysis\n(n = x - y - z)'
e1 <- 'Data linked with\nexternal dataset'
a2 <- ''
b2 <- 'Excluded because of\nexclusion criteria (n = y)'
c2 <- 'Excluded because of\nmissing values (n = z)'
d2 <- ''
e2 <- ''
#Create a node dataframe
ndf <- create_node_df(
n = 10,
label = c(a1, b1, c1, d1, e1, #Column 1
a2, b2, c2, d2, e2), #Column 2
style = c('solid', 'invis', 'invis', 'solid', 'solid', #Column 1
'invis', 'solid', 'solid', 'invis', 'invis'), #Column 2
shape = c('box', 'point', 'point', 'box', 'box', #Column 1
'plaintext', 'box', 'box', 'point', 'point'), #Column 2
width = c(3, 0.001, 0.001, 3, 3, #Column 1
2, 2.5, 2.5, 0.001, 0.001), #Column 2
height = c(1, 0.001, 0.001, 1, 1, #Column 1
1, 1, 1, 0.001, 0.001), #Column 2
fontsize = c(rep(14, 10)),
fontname = c(rep('Helvetica', 10)),
penwidth = 1.5,
fixedsize = 'true')
#Create an edge dataframe
edf <- create_edge_df(
from = c(1, 2, 3, 4, #Column 1
6, 7, 8, 9, #Column 2
2, 3 #Horizontals
),
to = c(2, 3, 4, 5, #Column 1
7, 8, 9, 10, #Column 2
7, 8 #Horizontals
),
arrowhead = c('none', 'none', 'normal', 'normal', #Column 1
'none', 'none', 'none', 'none', #Column 2
'normal', 'normal' #Horizontals
),
color = c('black', 'black', 'black', 'black', #Column 1
'#00000000', '#00000000', '#00000000', '#00000000', #Column 2
'black', 'black' #Horizontals
),
constraint = c(rep('true', 8), #Columns
rep('false', 2) #Horizontals
)
)
g <- create_graph(ndf,
edf,
attr_theme = NULL)
render_graph(g)
The result should look like this:
But instead it looks likes this when i run the code on my computer
Anyone eager to help?
Best regards,
H

Answer 1

Maybe a bit late, but better than never.
You have to create two nodes with width = 0 and height = 0, from where the arrows can origin horizontally. They need to be defined as subgraphs in order to be on a horizontal axis.
DiagrammeR::grViz("digraph prisma{
node [shape=box, fontsize = 12, fontname = 'Helvetica', width = 2];
a; b; c; d; e
# create 2 nodes without box around
node [shape = point, width = 0, height = 0]
x1; x2
graph [splines=ortho, nodesep=1, dpi = 72]
# Labels
a [label = 'Total available patients\n(n = x)'];
b [label = 'Excluded because of\nexclusion criteria (n = y)'];
c [label = 'Excluded because of\nmissing values (n = z)'];
d [label = 'Included for analysis\n(n = x - y - z)']
e [label = 'Data linked with\nexternal dataset']
# Edge definitions
a -> x1 [arrowhead='none']
x1 -> x2 [arrowhead='none']
x1 -> b
x2 -> c
x2 -> d
d -> e
# Make subgraph definition so arrow is horzontal
subgraph {
rank = same; b; x1;
}
subgraph {
rank = same; c; x2;
}
}
}
")
Created on 2021-08-06 by the reprex package (v2.0.1)
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