r - Problems with German Umlaut in RStudio (Windows 7) -

i have problems using umlauts in rstudio. first, .csv file read in this:

mydat<-read.csv("c:/mydat.csv",                     header=f,                     sep=";",                     na.strings= c("na","")) 

when open dataframe mydat, seems went fine:

but when use r-console, umlauts gone:

levels(mydat$v6) [1] "Öfter als fünfmal" "einmal" "zwei- bis fünfmal"  

i tried using read.table , encoding="windows-1252", doesn't change anything. on mac works fine.

here system. perhaps there's easy solution , i'm dumb, every other time posted question on stackoverflow.

sys.getlocale() [1] "lc_collate=german_germany.1252;lc_ctype=german_germany.1252;lc_monetary=german_germany.1252;lc_numeric=c;lc_time=german_germany.1252"  r.version                _                            platform       x86_64-w64-mingw32           arch           x86_64                       os             mingw32                      system         x86_64, mingw32              status                                      major          3                            minor          1.3                          year           2015                         month          03                           day            09                           svn rev        67962                        language       r                            version.string r version 3.1.3 (2015-03-09) nickname       smooth sidewalk