Plot multible networkD3-plots (Sanky) in a for loop


I am working on an Markdown project, where i need to plot multible networkD3 Sanky-network-plots in a for loop. But when i knit the poject to an html the plots wont show in the document. The wired part is when i call the function which generates the Sanky-Plot outside the for loop the results are shown.

Here i have made a very simple version of my code. (NOTE here the function MakeSanky dose nothing special and just returns the same plot for each i, for my case the function is in a different file with several parameters):


```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = FALSE)


MakeSanky <- function(year){
  links <- data.frame(
  source=c("group_A","group_A", "group_B", "group_C", "group_C", "group_E"), 
  target=c("group_C","group_D", "group_E", "group_F", "group_G", "group_H"), 
  value=c(2,3, 2, 3, 1, 3)
  # From these flows we need to create a node data frame: it lists every entities involved in the flow
  nodes <- data.frame(
    as.character(links$target)) %>% unique()
  # With networkD3, connection must be provided using id, not using real name like in the links dataframe.. So we need to reformat it.
  links$IDsource <- match(links$source, nodes$name)-1 
  links$IDtarget <- match(links$target, nodes$name)-1
  # Make the Network
  p <- sankeyNetwork(Links = links, Nodes = nodes,
                Source = "IDsource", Target = "IDtarget",
                Value = "value", NodeID = "name", 

title: "Test:"
output: bookdown::html_document2
chunk_output_type: console


year <- c("2014", "2015", "2018")

print("Here the plots are missing")
for(i in year){
  g <- MakeSanky(i)
print("This plots are shown correct")

As you can see if i call the function ouside the loop it works, if i call it inside the for loop no plots are shown. Maybe you can help me on this problem?

When using for loop in knitr you may need to call print explicitly on the object.

See example with table in 10.1 The function knitr::kable() | R Markdown Cookbook

Otherwise, you can use knit_child to iterate on a list and produce output to include in the document

Thank you for the hint with knit_child I finally managed to plot it. Even though I dont really know what you mean with the print(), because as you see in my code i already use print() inside the for loop ?

Oh I missed that. It means the basic print is not enough and probably a knit_print method comes into play.

With knitr printing object to be included into output document must sometimes be different that usual print.
Custom Print Methods

By using knit_child you ensure that the correct knitr tools are run correctly for the printing.

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