sp_execute_external_script R script 'unable to start png() device' - r

Question

I am trying to create a plot in SQL Server R using the sp_execute_external_script command, but it fails to create the plot png image:
DECLARE #stateName nvarchar(50) = 'Michigan'
EXEC sp_execute_external_script
#language = N'R',
#script = N'
covidWeeklyDataSet <- InputDataSet
# set up report file for chart
reportfile <- "C:\\temp\\Covid19-Weekly.png"
png(file = reportfile)
plot(x = covidWeeklyDataSet[, 1], y = covidWeeklyDataSet[, 2],
main = paste(state_name, "Weekly Covid 19 Counts", sep = ""),
col = 3, ylab = "Cases", xlab = "Dates", ylim = c(0, 35000))
par(new = TRUE)
plot(x = covidWeeklyDataSet[, 1], y = covidWeeklyDataSet[, 3],
col = 2, ylab = "Cases", xlab = "Dates", ylim = c(0, 35000))
dev.off()
',
#input_data_1 = N'SELECT [date], cases, deaths FROM #weekly',
#params = N'#state_name nvarchar(20)',
#state_name = #stateName
The error message is as follows:
Msg 39004, Level 16, State 20, Line 13 A 'R' script error occurred
during execution of 'sp_execute_external_script' with HRESULT
0x80004004. Msg 39019, Level 16, State 2, Line 13 An external script
error occurred: Error in png(file = reportfile) : unable to start
png() device Calls: source -> withVisible -> eval -> eval -> png In
addition: Warning messages: 1: In png(file = reportfile) : unable to
open file 'C:\temp\Covid19-Weekly.png' for writing 2: In png(file =
reportfile) : opening device failed
Error in execution. Check the output for more information. Error in
eval(ei, envir) : Error in execution. Check the output for more
information. Calls: runScriptFile -> source -> withVisible -> eval ->
eval -> .Call Execution halted
It also fails as an administrator. Please help.

Answer 1

READ & WRITE permissions for c:\temp to "ALL APPLICATION PACKAGES".
EXEC sp_execute_external_script
#language = N'R',
#script = N'
#file.create("c:\\temp\\mytest.png")
png(filename = "c:\\temp\\mytest.png",
width = 500, height = 500, units = "px", pointsize = 12,
bg = "white", res = NA)
x <- sample(c("A","B","C","D"), 20, replace=TRUE)
plot(table(x))
dev.off()'