How could I save a pixmap plot in R as a ".pgm" file?

I have generated a number of pixmapGrey files in rstudio, and I would like to save their plots as pgm images.

I am aware that one option is to save the plots as JPEG, PNG, TIFF, and BMP then, convert them to pgm.

What I really would like to know is whether there is a way to save the plots of pixmapGrey data as "PGM"?

for(i in 1:100){
Target <- pixmapGrey(X[i] ,nrow=150, ncol= 130) # X[i]s are vectors of length 19500
quartz()
plot(Target)

} ```