[R] quantiles on rows of a matrix

[Peter Ehlers]

On 2010-07-07 16:52, Jim Bouldin wrote:
>
> I'm trying to obtain the mean of the middle 95% of the values from each row
> of a matrix  (that is, the highest and lowest 2.5% of values in each row
> are removed before calculating the mean).  I am having all sorts of
> problems with this; for example the command:
>
> apply(matrix1,1,function(x) quantile(c(.05,.90),na.rm=T))
>
> returns the exact same quantile values for each row, which is clearly
> wrong.  But even if the values were right, I'm not sure how I would then
> translate those quantile values into another apply function to get the
> mean, since they differ from row to row.
>
> I also tried:
> apply(matrix,1,mean,na.rm=T,trim=.05))
> and the trim argument was simply ignored

I doubt that the 'trim' argument was ignored. If your
matrix is of sufficiently small dimensions, then trim
may not have any effect. Try trim=0.4 to see if it
makes a difference. (And you would probably want
trim=0.025 for your application.)

   -Peter Ehlers

>
>
> Stumped. Any help appreciated. Thanks.
>
>
> Jim Bouldin, PhD
> Research Ecologist
> Department of Plant Sciences, UC Davis
> Davis CA, 95616
> 530-554-1740
>
> ______________________________________________