[R] creating additional column

[Philipp Pagel]

	Hi!

max.col does what you want. Example:

> dat <- data.frame(a=rnorm(20),b=rnorm(20),c=rnorm(20))
> dat
             a           b          c
1   1.17910304 -0.56951219 -0.2243664
2  -1.43840866 -0.99013855 -0.1613536
3   1.08515152 -0.77975274  0.3734530
4  -0.92154605 -0.20318367  0.1384842
[...]
> dat$maxcol <- colnames(dat)[max.col(dat)]
> dat
             a           b          c maxcol
1   1.17910304 -0.56951219 -0.2243664      a
2  -1.43840866 -0.99013855 -0.1613536      c
3   1.08515152 -0.77975274  0.3734530      a
4  -0.92154605 -0.20318367  0.1384842      c
[...]

cu
	Philipp

On Tue, Mar 08, 2011 at 01:25:10PM +0100, Bodnar Laszlo EB_HU wrote:
> Hello everybody,
> 
> I have a little problem in good old R. It is basically the following.
> 
> I have this small database with 3 rows and the following columns:
> d1,
> d2,
> d3 and
> Highest d value - which selects the highest value from d1, d2, d3 in each row.
> 
> d1              d2              d3              Highest d value
> 1       51.398426       39.111721       11.6086220      51.398426
> 2       4.057801        7.728407        0.1234711       7.728407
> 3       7.279341        7.360509        18.2964676      18.296468
> 
> I'd like to make an additional column which shows the label of the relevant column where we've found the maximum d value. Something like this:
> 
> d1              d2              d3              Highest d value Where is the maximum?
> 1       51.398426       39.111721       11.6086220      51.398426       d1
> 2       4.057801        7.728407        0.1234711       7.728407        d2
> 3       7.279341        7.360509        18.2964676      18.296468       d3
> 
> Is there an easy way to do this?
> Thank you very much and have a pleasant day!
> 
> Laszlo
> 
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