df$varname is a column of df. df["varname"] is a one-column df containing that column.
df[["varname"]] is a column of df (same as df$varname). df[,"varname"] is a column of df (same as df$varname). df[,"varname",drop=FALSE] is a one-column df (same as df$varname). df$newVarname <- df["varname"] inserts a new component into df, the component being a one-column data.frame, not the column in that data.frame. Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: r-help-boun...@r-project.org > [mailto:r-help-boun...@r-project.org] On Behalf Of Albert-Jan Roskam > Sent: Friday, June 17, 2011 1:49 PM > To: R Mailing List > Subject: [R] is this a bug? > > Hello, > > Is the following a bug? I always thought that df$varname <- > does the same as > df["varname"] <- > > > df <- data.frame(weight=round(runif(10, 10, 100)), > sex=round(runif(100, 0, > 1))) > > df$pct <- df["weight"] / ave(df["weight"], df["sex"], FUN=sum)*100 > > names(df) > [1] "weight" "sex" "pct" ### ----------> ok > > head(df) > weight sex weight ### ----------> huh!?! > 1 86 0 2.4002233 > 2 19 1 0.5643006 > 3 32 0 0.8931063 > 4 87 0 2.4281328 > 5 45 0 1.2559308 > 6 95 0 2.6514094 > > rm(df) > > df <- data.frame(weight=round(runif(10, 10, 100)), > sex=round(runif(100, 0, > 1))) > > df["pct"] <- df["weight"] / ave(df["weight"], df["sex"], > FUN=sum)*100 ### > >-----> this does work > > names(df) > [1] "weight" "sex" "pct" > > head(df) > weight sex pct > 1 15 0 0.5246590 > 2 43 0 1.5040224 > 3 17 1 0.9284544 > 4 44 1 2.4030584 > 5 76 1 4.1507373 > 6 59 0 2.0636586 > > do.call(c, R.Version()) > platform arch > "i686-pc-linux-gnu" "i686" > os system > "linux-gnu" "i686, linux-gnu" > status major > "" "2" > minor year > "11.1" "2010" > month day > "05" "31" > svn rev language > "52157" "R" > version.string > "R version 2.11.1 (2010-05-31)" > > # Thanks! > > Cheers!! > Albert-Jan > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > All right, but apart from the sanitation, the medicine, > education, wine, public > order, irrigation, roads, a fresh water system, and public > health, what have the > Romans ever done for us? > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > [[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. > ______________________________________________ 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.
