Replicating pdf layout for png output with plot.drc

[Eike]

Hello,

I am trying to replicate images plotted into a pdf as png files. I use the drc package for data analysis and plot with this package.

Here is some example code:

library(drc)

#y values
y <- c(102.951595194603, 100.847607393735, 74.649218346333, 59.448852705819,
49.3273721230525, 28.2010422250102, 0, 101.496908554261, 83.3736997281258,
30.4407625786927, 33.9671793614587, 32.3082156692324, 27.2386746113449, 0)
#x values
x <- c(0.0274348422496571, 0.0823045267489712, 0.246913580246914,
0.740740740740741, 2.22222222222222, 6.66666666666667, 20, 0.0274348422496571,
0.0823045267489712, 0.246913580246914, 0.740740740740741, 2.22222222222222,
6.66666666666667, 20)

curve <- drm(y ~ x, fct = LL.3()) #create a curve based on data above

pdf('example.pdf', width = 28, height = 18 ) #start png plotting device with graphical parameters
par(xpd = F, #ablines are underneath boxplot
mar = par()$mar + c(10,12,7,7), #margins
mgp = c(3,4,0)) #what does this?
par(mfrow=c(1,1)) #plots x rows and y columns of images into pdf

plot(curve, lwd = 10) plot curve
box(lwd = 7) plot box around curve

TList <- list(T1 <- "Text 1", T2 <- "Text 2", T3 <- "Text 3") #create list of text segments to be plotted underneath each other
for(r in 1:length(TList)){ plot all segments...
ins <- (r-1)*0.05 #with some vertical distance from each other...
legend('topright', inset = c(0, ins), #at the topright
legend=paste('Box: ',TList[[r]], sep=''),
lwd=6, cex=3, box.lty=0)
}
dev.off() #close plot device

###repeat it for a png device

png('example.png', units = "in", res = 100, width = 28, height = 18)
par(xpd = F, #ablines are underneath boxplot
mar = par()$mar + c(10,12,7,7), #margins
mgp = c(3,4,0)) #what does this?
par(mfrow=c(1,1)) #plots x rows and y columns of images into png

plot(curve, lwd = 10) plot curve
box(lwd = 7) plot box around curve

for(r in 1:length(TList)){ plot all segments...
ins <- (r-1)*0.05 #with some vertical distance from each other...
legend('topright', inset = c(0, ins), #at the topright
legend=paste('Box: ',TList[[r]], sep=''),
lwd=6, cex=3, box.lty=0)
}
dev.off() #close plot device

As you can see, I have some x and y data. With this, I create a drm object ("curve" variable) with the drc function. When I plot the object and put some legends at the top right, everything looks just fine. But when I plot the same object under the same conditions as a png file, the legend does not look the same but has some overlay (see image below).

I was wondering if anyone can tell me, why this is the case and how to solve this issue. I also tried to go another route by simply converting the pdf file into pngs… but this does not work either. You can see my problem here: Converting a pdf into several pngs

So, does anyone ave an idea, how to perfectly replicate the pdf layout?

Thanks, br,

Eike