use function to plot in shiny - r

Question

I use a function to plot in R, because this is pretty large code for the plot (hexagonals etc). For the sake of neat code I put this in a function.
It is about a SOM algorithm , that does not really matter for now, but I create the data I need, then I normally plot it with the following code:
mydata <- som_model$codes
var <- 1
title <- names(som_model$data)[var]
dataplot <- matrix(mydata[,var],nrow=gridsize,ncol=gridsize,byrow=TRUE)
source('plotHexMap.R')
plotHexMap(dataplot,title,gridsize)
So now I want to do this in Shiny:
observe({
if(input$plottrained>0){
var <- 1
title <- names(som_model$data)[var]
dataplot<-matrix(mydata[,var],nrow=gridsize,ncol=gridsize,byrow=TRUE)
source("plotHexMap.R")
output$plot1 <-renderPlot({plotHexMap(dataplot,title,gridsize)})
}
})
Ok so this does not work, but when I just write the plot to a global variable (with <<-) it does exist and I can see it in the plots, so by doing this:
observe({
if(input$plottrained>0){
var <- 1
title <- names(som_model$data)[var]
dataplot<-matrix(mydata[,var],nrow=gridsize,ncol=gridsize,byrow=TRUE)
source("plotHexMap.R")
plot1 <<-renderPlot({plotHexMap(dataplot,title,gridsize)})
}
})
What am I missing here? what does shiny need that normal R environment does not to plot this from function?
would really appreciate any help with this! Thanks in advance,
Pieter

Answer 1

Instead of observe, try renderPlot in server:
output$myplot <- renderPlot({
if(input$plottrained>0){
var <- 1
title <- names(som_model$data)[var]
dataplot<- matrix(mydata[,var],nrow=gridsize,ncol=gridsize,byrow=TRUE)
source("plotHexMap.R", local = TRUE) #assuming this file is actually local for you
plot1 <- plotHexMap(dataplot,title,gridsize)
}
else{return(NULL)}
})
And then plotOutput in the ui:
plotOutput('myplot')