[R] is this a bug?

[William Dunlap]

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-bounces at r-project.org 
> [mailto:r-help-bounces at 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
> 
> 
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> health, what have the 
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