Hi Vincy, have you checked names(df2)
and names(df_new) because by default 'data.frame' checks the column names "to ensure that they are syntactically valid variable names" and 1w and 2w aren't, so an X is prepended (see ?data.frame and ?make.names). compare tst.fail<-data.frame(a=1:3,"1a"=1:3,"1b"=1:3) names(tst.fail) #and tst<-data.frame(a=1:3,"1a"=1:3,"1b"=1:3,check.names = F) names(tst) this works for me: tst2<-data.frame(a=1:3,w1=4:6,w3=4:6) write.csv(merge(tst,tst2),file="testr.csv") hth. Am 19.07.2012 08:55, schrieb Vincy Pyne: > Dear R helpers, > > I have one trivial problem while writing an output file in csv format. > > I have two dataframes say df1 and df2 which I am reading from two different > csv files. > > df1 has column names as date, r1, r2, r3 while the dataframe df2 has column > names as date, 1w, 2w. > > (the dates in both the date frames are identical also no of elements in each > column are equal say = 10). > > I merge these dataframes as > > df_new = merge(df1, df2, by = "date", all = T) > > So my new data frame has columns as > > date, r1, r2, r3, 1w, 2w > > However, if I try to write this new dataframe as a csv file as > > write.csv(data.frame(df_new), 'df_new.csv', row.names = FALSE) > > The file gets written, but when I open the csv file, the column names > displayed are as > > date, r1, r2, r3, X1w, X2w > > My original output file has about 200 columns so it is not possible to write > column names individually. Also, I can't change the column names since I am > receiving these files from external source and need to maintain the column > names. > > Kindly guide > > > Regards > > Vincy > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > -- Eik Vettorazzi Department of Medical Biometry and Epidemiology University Medical Center Hamburg-Eppendorf Martinistr. 52 20246 Hamburg T ++49/40/7410-58243 F ++49/40/7410-57790 -- Pflichtangaben gemäß Gesetz über elektronische Handelsregister und Genossenschaftsregister sowie das Unternehmensregister (EHUG): Universitätsklinikum Hamburg-Eppendorf; Körperschaft des öffentlichen Rechts; Gerichtsstand: Hamburg Vorstandsmitglieder: Prof. Dr. Guido Sauter (Vertreter des Vorsitzenden), Dr. Alexander Kirstein, Joachim Prölß, Prof. Dr. Dr. Uwe Koch-Gromus ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.