On 11-01-13 6:26 AM, Rainer M Krug wrote:> -----BEGIN PGP SIGNED MESSAGE-----
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>
> Hi
>
> Assuming the following:
>
>> x<- data.frame(a=1:10, b=runif(10))
>> str(x)
> 'data.frame': 10 obs. of 2 variables:
> $ a: int 1 2 3 4 5 6 7 8 9 10
> $ b: num 0.692 0.325 0.634 0.16 0.873 ...
>> write.csv(x, "x.csv")
>> x2<- read.csv("x.csv")
>> str(x2)
> 'data.frame': 10 obs. of 3 variables:
> $ X: int 1 2 3 4 5 6 7 8 9 10
> $ a: int 1 2 3 4 5 6 7 8 9 10
> $ b: num 0.692 0.325 0.634 0.16 0.873 ...
>>
>
> Using the two functions write.csv and read.csv, I would assume, that the
> resulting data.frame x2 be identical with x, but it has an additional
> column X, which contains the row names of x.
>
> I know read.table and write.table which work as expected, but I would
> like to use a csv for data exchange reasons.
>
> I know that I can use
> write.csv(x, "x.csv", row.names=FALSE)
>
> and it would work, but shouldn't that be the default behaviour?
I don't think so. The CSV format is an export format which holds less
information than a dataframe. By exporting the dataframe to CSV and
importing the result, you are discarding information and you should
expect to get something different.
If you want to save a dataframe to disk and read it back unchanged, you
should use save() and load().
Duncan Murdoch
> And if this is not compliant with csv files, shouldn't the function
> read.csv convert the first column into the row names?
>
> Cheers,
>
> Rainer
>
> - --
> Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
> Biology, UCT), Dipl. Phys. (Germany)
>
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