TeachingDemos: using etxtPlot with numerical results in loops - r

Question

When running this code:
library(TeachingDemos)
etxtStart(dir=getwd(), file="Nofunciona.txt")
etxtComment('Just a test')
for(i in 1:10){
cat("###",i,":\n")
my.sample = sample(100)
print(summary(my.sample))
qqnorm(my.sample)
etxtPlot(width=7.5)
}
etxtStop()
I only get a file named "Nofunciona.txt" with a text line "Just a test" and the commands to include the graphs, but nothing about the results of cat() or print(summary()), although I can see the results on the console.
If I change the loop using these two loops:
for(i in 1:10){
cat("###",i,":\n")
my.sample = sample(100)
print(summary(my.sample))
}
for(i in 1:10){
qqnorm(my.sample)
if(archivo) etxtPlot(width=7.5)
}
etxtStop()
Then I can obtain a file with the text results of cat(), and summary() and also the commands to include the graphs at the end. I know that with the last for loop I obtain ten times the same graph, that is not relevant.
It seems I cannot obtain graphical results and text results at the same time inside a for loop. Why does not the first code work?
Any idea?
Thanks.

Answer 1

The reason that is happening is because it is assumed that you do not want the etxtPlot command to show up in the transcript or command history, so when that function is called it sets a variable that tells the workhorse internal function (that is called by the task manager) to skip outputting the commands and results temporarily. This works correctly outside of a loop because the suppression of the output only lasts for the call to etxtPlot and everything else is properly output. The problem comes when you do this in a loop, everything done in the loop is processed in a single step (see ?addTaskCallback for the details on how things are handled), so the suppressing of the command and output from etxtPlot ends up also suppressing the commands and output from everything else in the loop.
A possible work around is to run the command:
trace(etxtPlot, edit=TRUE)
Then change the TRUE to FALSE in the second to last line of the code. Now you will see all the commands and output (including the calls to etxtPlot), but the plots will all come before the output (because the commands to include the plots are inserted at each iteration, but the other output is inserted after the loop has completed).
You might consider using the knitr package as an alternative, specifically the stitch or spin functions if you don't want to create a full template file, but just have some code processed. They don't do the realtime transcript, but deal better with automatic plot insertion.