I am trying to solve the following problem using the mmap package:
1.) Store some data as a memory mapped file that resides on the disk.
2.) Open the data and add some new data (or change it) to that file.
1.) works fine using the following code:
cFile <-tempfile()
dfrData <- data.frame(matrix(data=1, ncol=2, nrow=10))
mmapData <- as.mmap(dfrData, file=cFile)
stcData <- mmapData$storage.mode
munmap(mmapData)
2.) Now I want to link mmapAfter to the file that should still reside as cFile,
or? What is the problem here? The error I get is at the second line of the
code: "
Error in if (!x$bytes) stop("no data to extract") : missing value where
TRUE/FALSE needed".
mmapAfter <- mmap(cFile, mode=stcData, extractFUN=as.data.frame)
mmapAfter[];
mmapAfter [1,2] <- 2;
mmapAfter [];
munmap(mmapAfter)
I also noted when I execute the following code that
the mmapData$filedesc doesn't show the filename I specified in cFile. Is this
not how it is supposed to be used?
cFile <- 'C:/temp/testmapfile'
dfrData <- data.frame(matrix(data=1, ncol=2, nrow=10))
mmapData <- as.mmap(dfrData, file=cFile)
mmapData$filedesc
Thanks for your help.
Regards,
Wolfgang Wu
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