[R] writeMat error

[Henrik Bengtsson]

Hi,  a follow up on this as well: I've fixed the below bug in
writeMat().  R.matlab v1.2.4 is now available on CRAN.  Please update.

Henrik


On Wed, Oct 1, 2008 at 12:55 PM, Henrik Bengtsson <hb at stat.berkeley.edu> wrote:
> Hi.
>
> On Sat, Sep 27, 2008 at 5:17 AM, Steele, Dr Douglas <d.steele at abdn.ac.uk> wrote:
>> Hi
>>
>> I am using Ubuntu 8.04 64 bit, R as below, Matlab 7.6.0.  I would like to transfer mat files back and forward between R and Matlab.  Whilst I have used Matlab for years its been a long time since I have used R (hence question may be a bit simple)
>>
>> Running code
>>
>> A  <-  c(1:10)
>> dim(A) <- c(2,5)
>> library(R.matlab)
>> writeMat('A.mat', A=A)
>>
>> Does not appear to generate any mat file either in local directory or in /tmp/R*
>
> It *is* created in the *current* directory.  If there are no errors,
> then it should be there.  Use can use getwd() to see which this is,
> e.g.
>
> library("R.matlab");
> A  <-  c(1:10);
> dim(A) <- c(2,5);
> writeMat("A.mat", A=A);
> print(getwd());
>
> [1] "C:/Users/foo/braju.com.R/R.matlab"
>
> print(list.files())
> [1] "A.mat"
>
> res <- readMat("A.mat");
>> str(res)
> List of 1
>  $ A: int [1:2, 1:5] 1 2 3 4 5 6 7 8 9 10
>  - attr(*, "header")=List of 3
>  ..$ description: chr "MATLAB 5.0 MAT-file, Platform: windows,
> Software: R v2.7.2, Created on: Wed Oct 01 12:40:23 2008
>             "
>  ..$ version    : chr "5"
>  ..$ endian     : chr "little"
>
>>
>> I tried both current version of R.matlab and older version because of bug
>> https://stat.ethz.ch/pipermail/r-help/2008-September/173432.html
>
> Correct.  You should use install the old R.matlab v1.2.1, because
> v1.2.3 (as well as v1.2.2) contains a bug which is still to be fixed.
>
>>
>> A <- matrix(1:27, ncol=3)
>> B <- as.matrix(1:10)
>> fn <- paste(tempfile(), ".mat", sep="")
>> writeMat(fn, A=A, B=B)
>> data <- readMat(fn)
>> print(data)
>> unlink(fn)
>
> This is from example(writeMat).  It works this far, correct?  You
> should see 'data' being reported.  The unlink() command is there such
> that the example script cleans up after itself, i.e. it delete the
> temporary MAT file. Skip that last command if you want to grab the
> file.
>
>> onWrite <- function(x)
>> writeBin(x$length, con=x$con, size=4, endian="big");
>> writeMat(fn, A=A, B=B, onWrite=onWrite)
>
> Do *not* use these latter commands.  They are modifications of
> original example code that is only used to illustrate for advanced
> users how to send a MAT structure over a connection.  As indicated by
> the example code:
>
>     ## Not run:
>     # When writing to a stream connection the receiver needs to know in
>     # beforehand how many bytes are available. This can be done by using
>     # the 'onWrite' argument.
>     onWrite <- function(x)
>       writeBin(x$length, con=x$con, size=4, endian="little");
>     writeMat(con, A=A, B=B, onWrite=onWrite)
>     ## End(Not run)
>
> they are within a "Not run" block, which in R means that they are not
> necessarily intended to be executed.  If you run the example code with
> example(writeMat) that code will not be executed.  You obviously
> cut'n'paste here, but didn't you see the above comments.  How you do
> view you help(), i.e. typically help(writeMat) will display those
> comments?  FYI, the first argument 'con' (supposed to indicate a
> connection) is on purpose non-existing and not the same as the 'fn'
> argument (pathname) in the preceeding code.
>
>>
>> Does generate a file in /tmp/Rtmpjhfjxw
>> -rw-r--r--  1 dst dst  396 2008-09-27 12:46 file643c9869.mat
>>
>> When I try to read it into Matlab I get
>>
>> ??? Error using ==> load
>> Unable to read MAT-file /tmp/Rtmpjhfjxw/file643c9869.mat
>>
>> File may be corrupt.
>
> Yes, but that is because you use that latter code.  Before writing the
> MAT structure, it writes the byte size of the structure to the file,
> which is not part of the MAT file format.  You don't want this.  This
> is only intended for sending MAT structure over a connection.
>
>>
>> (This is same error message as above link and occurs with old and current version of R.matlab)
>>
>> Any advice would be very helpful
>
> Hope this helps
>
> Henrik
>
>>
>> Regards
>>
>> Douglas
>>
>>
>>
>>> sessionInfo()
>> R version 2.6.2 (2008-02-08)
>> x86_64-pc-linux-gnu
>>
>> locale:
>> LC_CTYPE=en_GB.UTF-8;LC_NUMERIC=C;LC_TIME=en_GB.UTF-8;LC_COLLATE=en_GB.UTF-8;LC_MONETARY=en_GB.UTF-8;LC_MESSAGES=en_GB.UTF-8;LC_PAPER=en_GB.UTF-8;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_GB.UTF-8;LC_IDENTIFICATION=C
>>
>> attached base packages:
>> [1] stats     graphics  grDevices utils     datasets  methods   base
>>
>> other attached packages:
>> [1] R.matlab_1.2.1    R.oo_1.4.6        R.methodsS3_1.0.3
>>
>> loaded via a namespace (and not attached):
>> [1] rcompgen_0.1-17
>>>
>>
>>
>> The University of Aberdeen is a charity registered in Scotland, No SC013683.
>>
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>