plotpng <- function(fnargs){
CONTENTTYPE <- "image/png";
mytempfile <- do.call(doplotpng, fnargs);
return(list(filename = mytempfile, type = CONTENTTYPE));
}
doplotpng <- function(`#dofn`, `!width` = 640, `!height` = 480, `!units` = "px", `!pointsize` =12, `!printoutput`= TRUE, ...){
#prepare
mytempfile <- tempfile();
png(mytempfile, width=`!width`, height=`!height`, units=`!units`, pointsize=`!pointsize`);
par("bg" = "white")
# The code below works fine. However, hadley's method results in a smaller 'call' object for the
# resulting object.
#
# e1 <- new.env(parent = .GlobalEnv)
# output <- eval(get("#dofn")(...), envir=e1);
#build the function call and evaluate expressions at the very last moment.
fnargs <- as.list(match.call(expand.dots=F)$...);
argn <- lapply(names(fnargs), as.name);
names(argn) <- names(fnargs);
#insert expressions into call
exprargs <- sapply(fnargs, is.expression);
if(length(exprargs) > 0){
expressioncalls <- lapply(fnargs[exprargs], "[[", 1);
argn[names(fnargs[exprargs])] <- expressioncalls;
}
#call the new function
if(is.character(`#dofn`)){
mycall <- as.call(c(list(parse(text=`#dofn`)[[1]]), argn));
} else {
mycall <- as.call(c(list(as.name("FUN")), argn));
fnargs <- c(fnargs, list("FUN" = `#dofn`));
}
output <- eval(mycall, fnargs, globalenv());
if(`!printoutput`){
void <- capture.output(print(output));
}
#write output
dev.off();
#check if something as generated
if(!file.exists(mytempfile)){
stop("This call did not generate any plot. Make sure the function/object produces a graph.")
}
return(mytempfile)
}
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