[R] how to get colnames of a dataframe within a function called by 'apply'

[Gabor Grothendieck]

One other comment.  A for loop would seem to be
appropriate here since you are not using the result
of sapply anyways:

par.or <- par(mfrow = c(3,3))

for(n in colnames(temp)) {
  qqnorm(temp[,n], main = n)
  qqline(temp[,n], col = "red")
}

par(par.or)


On 10/28/05, Gabor Grothendieck <ggrothendieck at gmail.com> wrote:
> Iterate over the column names rather than the columns themselves:
>
> par.or <- par(mfrow=c(3,3))
> nv <- function(name, data) {
>        qqnorm(data[,name], main=name)
>        qqline(data[,name], col="red")
>        invisible()
> }
> sapply(colnames(temp), nv, data = temp)
> par(par.or)
>
>
> On 10/28/05, Leo Gürtler <leog at anicca-vijja.de> wrote:
> > Hello alltogether,
> >
> > how is it possible to assign the colnames of a data.frame to a function
> > called by apply, e.g. for labeling a plot?
> > Example: I want to plot several qqnorm-plots side by side and there
> > should be a maintitle for each qqnorm-plot which is identical to the
> > respective colname.
> > I checked, but the column which is processed by the function called by
> > apply does not contain a colname (because by using str() it seems it is
> > no column at this point, but just a e.g. numerical vector).
> > I also tried with colnames() from within the function, but was not
> > successful to get the apropriate colname - either the whole string or
> > just the first one.Thus it lacks of a counter that contains the number
> > of the row which is processed.
> >
> > Here is an example code:
> >
> > <---snip--->
> >
> > nv <- function(xno.na)
> > {
> >  par.or <- par(mfrow=c(3,3))
> >  qqnorm(xno.na, main="HERE SHOULD BE THE NAME OF THE COLUMN")
> >  qqline(xno.na, col="red")
> >  par(par.or)
> >  print(str(xno.na))
> > }
> >
> >  > temp # just a part of the whole data.frame
> >        klarb1    klarb2 abarb laut skla1 skla2
> > a      NA 13.068182   7.5    4   0.5   0.5
> > b      NA  6.818182   9.0    6    NA   0.5
> > c      15.11628  6.818182  10.0    4   1.0   1.5
> > d      NA 18.181818  19.0    2   1.0   0.5
> >
> >  > apply(temp,2,nv)
> >
> > </---snip--->
> >
> >
> > Thanks a lot!
> >
> > best wishes,
> >
> > leo
> >
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