Using a list as multidimensional indexer
On Thu, 20 Jan 2011, Nick Sabbe wrote:
Hello list.
Another 'puzzle' for which I don't have a clean solution.
Say I have a multidimensional object, e.g.:
Mm<-matrix(1:6, nrow=2, dimnames=list(c("a","b"), c("g","h","i")))
And on the other hand I have a list
Ind<-list("b","g")
This holds, for each dimension, an indexer for that dimension.
Now I would like to get the element pointed at by the list.
The obvious solutions don't seem to work, and I can't seem to get do.call to
call the indexer ('[') on my multidimensional object.
Any suggestions?
do.call(`[`, c(quote(Mm), Ind))
[1] 2
do.call(`[`, c(list(Mm), Ind))
[1] 2 gives
Mm["b", "g"]
[1] 2 The first refers to the object by name, the second uses it directly.
Thanks in advance, Nick Sabbe -- ping: nick.sabbe at ugent.be link: http://biomath.ugent.be
Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595