And the extra twist in the tale is exemplified by this mini-version of Albert-Jan's first example:
DF <- data.frame(A=c(1,2,3)) DF$B <- c(4,5,6) DF$C <- c(7,8,9) DF # A B C # 1 1 4 7 # 2 2 5 8 # 3 3 6 9 DF$D <- DF["A"]/DF["B"] DF # A B C A # 1 1 4 7 0.25 # 2 2 5 8 0.40 # 3 3 6 9 0.50 ##And why: DF["A"]/DF["B"] # A # 1 0.25 # 2 0.40 # 3 0.50 ##So the ratio DF["A"]/DF["B"] comes out with the name of ##the numerator, "A". This is then the name given to DF$D Thus Albert-Jan's df["weight"] / ave(df["weight"], df["sex"], FUN=sum)*100 comes through with name "weight". Ted. On 17-Jun-11 21:06:42, William Dunlap wrote: > 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. -------------------------------------------------------------------- E-Mail: (Ted Harding) <ted.hard...@wlandres.net> Fax-to-email: +44 (0)870 094 0861 Date: 17-Jun-11 Time: 22:24:41 ------------------------------ XFMail ------------------------------ ______________________________________________ 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.
