[R] Moving data between R and Matlab back and forth?

[Tribo Laboy]

I realized that not everyone has Matlab and that basically the issue
is purely how to deal with the returned data in R, so I have revised
my example code and made it easier to copy-paste and run:


#Make a data frame in R

Maker <- factor(c("HP", "HP", "Sony", "DELL", "whitebox", "whitebox"))
CPUspeed <- c(2,4,2.5,2.5,2,5)
HDD <- c(80, 250, 100, 100, 80, 300)
RAM <- c(2, 2, 1, 2, 2, 4)
labpc <- data.frame(Maker, CPUspeed, HDD, RAM)
labpc

#Save in Matlab v6 format with 'writeMat'

library(R.matlab)
writeMat("labpc.mat", labpcexport = labpc)

#Load the file in R with 'readMat'

labpcfile <- readMat("labpc.mat")
labpcimport <- labpcfile$labpcexport
labpcimport

# This is the last line output
#, , 1
#
#         [,1]
#Maker    List,6
#CPUspeed Numeric,6
#HDD      Numeric,6
#RAM      Numeric,6

Now, how do I convert the result held in labpcimport back to a data frame?

Thanks in advance,

TL

On Thu, Mar 27, 2008 at 1:27 AM, Tribo Laboy <tribolaboy at gmail.com> wrote:
> Hi to the list,
>
>  I am trying to find a way to painlessly move structured data back and
>  forth between R and Matlab (also Octave). For this purpose I found the
>  R.matlab package great help. I wish to use a Matlab -v6 MAT file as an
>  intermediary format, because it is well read by both Matlab and
>  Octave. It is also well read by 'readMat' function in R.matlab
>  package, but that is where I run into problems because of poor
>  knowledge of R.
>
>  By structured data I mean data in data frames in R and the closest
>  equivalent - structures in Matlab. Here is what I have done.
>
>  -----------------------------------------------------
>  Make a data frame in R and export it
>  -----------------------------------------------------
>
>  > Maker <- factor(c("HP", "HP", "Sony", "DELL", "whitebox", "whitebox"))
>  > CPUspeed <- c(2,4,2.5,2.5,2,5)
>  > HDD <- c(80, 250, 100, 100, 80, 300)
>  > RAM <- c(2, 2, 1, 2, 2, 4)
>  > labpc <- data.frame(Maker, CPUspeed, HDD, RAM)
>
>  > labpc
>      Maker CPUspeed HDD RAM
>  1       HP      2.0  80   2
>  2       HP      4.0 250   2
>  3     Sony      2.5 100   1
>  4     DELL      2.5 100   2
>  5 whitebox      2.0  80   2
>  6 whitebox      5.0 300   4
>
>  > library(R.matlab)
>  > writeMat("labpc.mat", labpcdata = labpc)
>  --------------------------------------------------------------
>
>  --------------------------------------------------------------
>  In MATLAB - everything is as expected
>  --------------------------------------------------------------
>  load('labpc.mat')
>
>  >> labpcdata
>
>  labpcdata =
>
>        Maker: {6x1 cell}
>     CPUspeed: [6x1 double]
>          HDD: [6x1 double]
>          RAM: [6x1 double]
>
>  >> class(labpcdata)
>
>  ans =
>
>  struct
>
>  >> labpcstruct = labpcdata
>  >> save('labpcstruct.mat', 'labpcstruct')
>  ---------------------------------------------------------
>
>
>  -------------------------------------------------------
>  Back in R - how to rebuild the data frame from the list labpcstruct?
>  -------------------------------------------------------
>  > labpcfile <- readMat("labpcstruct.mat")
>  > labpcfile
>  $labpcstruct
>  , , 1
>
>          [,1]
>  Maker    List,6
>  CPUspeed Numeric,6
>  HDD      Numeric,6
>  RAM      Numeric,6
>
>
>  attr(,"header")
>  attr(,"header")$description
>  [1] "MATLAB 5.0 MAT-file, Platform: PCWIN, Created on: Wed Mar 26
>  15:49:21 2008                                                  "
>
>  attr(,"header")$version
>  [1] "5"
>
>  attr(,"header")$endian
>  [1] "little"
>
>  > labpcstruct <- labpcfile$labpcstruct
>  > labpcstruct
>  , , 1
>
>          [,1]
>  Maker    List,6
>  CPUspeed Numeric,6
>  HDD      Numeric,6
>  RAM      Numeric,6
>
>
>  > typeof(labpcstruct)
>  [1] "list"
>
>  --------------------------------------------
>
>  So if there is any kind soul that will tell me how to get back the
>  original data frame from the imported list 'labpcstruct', that would
>  be great.
>
>  Regards,
>
>  TL
>