Hi! I've done a merging between 2 dataframes using merge(): delme <- merge(miDUNS50peqB,Bnomscodmunicipis,by.x="POBLACION",by.y="NOMMUNI",all.x=T,sort=F) After realizing some problems in the resulting dataset, I've found that the problem was that, in some cases, there was no match between the by.x and the by.y elements, despite the fact that, apparently, such matching should exist. Specifically, I get no match for the cases in which both the by.x and the by.y variables are equal to "SANT VICEN? DELS HORTS". In the following example I select fields POBLACION and NOMMUNI in two cases for which both fields should be identical to "SANT VICEN? DELS HORTS" and I get: (082634 is the municipality code for that town in Bnomscodmunicipis and 08620 is the postal code for that town in delme) > x <- Bnomscodmunicipis[Bnomscodmunicipis$CODMUN=="082634",1][1] > y <- miDUNS50peqB[miDUNS50peqB$CODPOSTAL=="08620","POBLACION"][1] > str(x) chr "SANT VICEN? DELS HORTS" > str(y) chr "SANT VICEN? DELS HORTS" > x==y [1] FALSE which I cannot understand. If I just cut and paste those values and run the equivalent logical operation:> "SANT VICEN? DELS HORTS" == "SANT VICEN? DELS HORTS"[1] TRUE The problem is that the values for "SANT VICEN? DELS HORTS" in the resulting merged dataframe are wrong. Any help with this issue would be greatly appreciated, I'm really astonished. I think it might involve an encoding problem with the non-ascii characters, but don't get to see it. I'm using R 2.8.1 on ubuntu 8.04 (in english; And R is in English too) Agus -- Dr. Agustin Lobo Institut de Ciencies de la Terra "Jaume Almera" (CSIC) LLuis Sole Sabaris s/n 08028 Barcelona Spain Tel. 34 934095410 Fax. 34 934110012 email: Agustin.Lobo at ija.csic.es http://www.ija.csic.es/gt/obster