how to assign the title to the flowchart generated using DiagrammeR

could you please suggest a way to assign the title to the consort diagram generated using DiagrammeR package. Also i tried to color the boxes of all the nodes using fillcolor=blue in the node, but that does not seem to work,

library(tidyCDISC)
library(tidyverse)
library(ggalluvial)
library(DiagrammeR)


data('adsl', package='tidyCDISC')

# randomized population
pop1 <- adsl %>% rename_all(tolower) %>% filter(saffl=='Y') %>% count() %>% 
  mutate(col1=paste0('Safety Population\n(N=',n,')'))

popt <- adsl %>% rename_all(tolower) %>% filter(saffl=='Y') %>% group_by(trt01a) %>% count() %>% 
  mutate(col1=paste0(trt01a,'\n(N=',n,')'))

DiagrammeR::grViz("
              digraph box  {
               graph [layout=dot, overlap = true, fontsize = 10]
               
               node [shape=box, fontname = Helvetica, color = blue, fillcolor = red]
               
               total_population [label = '@@1']; 
               placebo [label = '@@2'];
               xanomeline_low_dose [label = '@@3'];
               xanomeline_high_dose [label = '@@4'];
              
               
               total_population  -> placebo total_population -> xanomeline_low_dose total_population -> xanomeline_high_dose 
               
                            }
              
              [1]:  pop1$col1 
              [2]:  popt$col1[1]
              [3]:  popt$col1[3]
              [4]:  popt$col1[2]
             
                  ")

Solution

For the title see How do you center a title for a diagram output to SVG using dot? or search the graphviz docs at https://graphviz.org. To get different fontsizes for the title and node labels, set different fontsize values in the graph and node declarations.`

To fill you need to set style=filled in the node declaration (or the individual node instantiations); again see the docs

Your example (without the extra packages) and code additions indicated by comments:

library(DiagrammeR)

var = 1:4
DiagrammeR::grViz("
              digraph box  {
              
                    graph [label = 'Main title', # title
                           labelloc='t';         # title location at 't'op
                           layout=dot, 
                           overlap = true, 
                           fontsize = 20]        # title fontsize
                    
                    node [shape=box, 
                          fontname = Helvetica, 
                          color = blue, 
                          style = filled,        # set node style to filled 
                          fillcolor = red, 
                          fontsize = 10]         # node label fontsize
                    
                    total_population [label = '@@1']; 
                    placebo [label = '@@2'];
                    xanomeline_low_dose [label = '@@3'];
                    xanomeline_high_dose [label = '@@4'];
                    
                    total_population  -> placebo total_population -> 
                    xanomeline_low_dose total_population -> xanomeline_high_dose 
                    }

                   [1]:  var[1]
                   [2]:  var[2]
                   [3]:  var[3]
                   [4]:  var[4]
                 ")