I need to create a pdf file with several chart created by ggplot2 arranged in a A4 paper, and repeat it 20-30 times.

I export the ggplot2 chart into ps file, and try to PostScriptTrace it as instructed in grImport, but it just keep giving me error of "Unrecoverable error, exit code 1".

I ignore the error and try to import and xml file generated into R object, give me another error:

attributes construct error

Couldn't find end of Start Tag text line 21

Premature end of data in tag picture line 3

Error: 1: attributes construct error

2: Couldn't find end of Start Tag text line 21

3: Premature end of data in tag picture line 3

What's wrong here?

Thanks!