Unexpected behaviour of write.csv - read.csv
On 11-01-13 6:26 AM, Rainer M Krug wrote:
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 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) Centre of Excellence for Invasion Biology Natural Sciences Building Office Suite 2039 Stellenbosch University Main Campus, Merriman Avenue Stellenbosch South Africa Tel: +33 - (0)9 53 10 27 44 Cell: +27 - (0)8 39 47 90 42 Fax (SA): +27 - (0)8 65 16 27 82 Fax (D) : +49 - (0)3 21 21 25 22 44 Fax (FR): +33 - (0)9 58 10 27 44 email: Rainer at krugs.de Skype: RMkrug -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk0u4X8ACgkQoYgNqgF2egrLIgCeIqAevHGcOAK56qPcpNJ+vWav iF0An2pk1RsY1GLJbvdMHG7FFpx437gB =d5aG -----END PGP SIGNATURE-----
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