[R] use of writePNG() in a multiplot OR rasterImage() size control in a multiplot

[Gygli, Gudrun]

Dear All,


I am trying to plot several things in a multiplot using par(mfrow...) AND add a pre-existing png file to that plot.

I have found 2 options of doing this in the web:


writePNG() and another fix using rasterImage().


writePNG(): the option using writePNG() does not add the  " pre-existing png" to my mutliplot.


    I use a code similar to this:

    img<-read("myotherpng.png")


    png(file="mydata.png")

    par(mfrow=c(1,3))

    plot(mydata)

    boxplot(mydata)

    writePNG(img, target="mydata.png")


    Any ideas why this does notwork?



rasterImage(): this is a bit more tricky, but works partly:


the code comes from the rforge (https://www.rforge.net/doc/packages/png/readPNG.html)

and writes the png (see detailed code at the end of email), but is basically:


    img<-read("myotherpng.png")


    png(file="mydata.png")

    par(mfrow=c(1,3))

    plot(mydata)

    boxplot(mydata)
    rforgecode using rasterImage() to print img



If I use this code like below, I do get the" pre-existing png" plotted in my multiplot, but with very wrong dimensions.

rasterImage(image, xleft, ybottom, xright, ytop)

I have no idea how to get the xleft, ybottom,xright and ytop values that match the file I import and allow plotting it fitting into the space allocated by mfrow (meaning that the plot, boxplot and image do not overlap.)


Any ideas?


Thanks for any help about the topic.


Best regards


Gudrun



    img<-read("myotherpng.png")


    png(file="mydata.png")

    par(mfrow=c(1,3))

    plot(mydata)

    boxplot(mydata)

if (exists("rasterImage")) { # can plot only in R 2.11.0 and higher
  plot(1:2, type='n')
  if (names(dev.cur()) == "windows") {
    # windows device doesn't support semi-transparency so we'll need
    # to flatten the image
    transparent <- img[,,4] == 0
    img <- as.raster(img[,,1:3])
    img[transparent] <- NA
    # interpolate must be FALSE on Windows, otherwise R will
    # try to interpolate transparency and fail
    rasterImage(img, 1.2, 1.27, 1.8, 1.73, interpolate=FALSE)
  } else {
    # any reasonable device will be fine using alpha
    rasterImage(img, 1.2, 1.27, 1.8, 1.73)
  }
}



Gudrun Gygli, MSc

PhD candidate

Wageningen University
Laboratory of Biochemistry
Dreijenlaan 3
6703 HA Wageningen
The Netherlands

Phone  31 317483387
e-mail: gudrun.gygli at wur.nl

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Project information: http://www.wageningenur.nl/en/show/Bioinformatics-structural-biology-and-molecular-modeling-of-Vanillyl-Alcohol-Oxidases-VAOs.htm