[R] Multiple conditional without if [Broadcast]

[Liaw, Andy]

From: bunny, lautloscrew.com
> 
> Dear all,
> 
> i am stuck with a syntax problem.
> 
> i have a matrix which has about 500 rows and 6 columns.
> now i want to kick some data out.
> i want create a new matrix which is basically the old one 
> except for all entries which have a 4 in the 5 column AND a 1 
> in the 6th column.
> 
> i tried the following but couldn´t get a new matrix, just some wierd
> errors:
> 
> newmatrix=oldmatrix[,2][oldmatrix[,5]==4]&&oldmatrix[,2][oldmatrix[,6]
> ==1]
> 
> all i get is:
> numeric(0)

That's not a `weird error', but a numeric vector of length 0.
 
> does anybody have an idea how to fix this one ?

Try:

newmatrix = oldmatrix[oldmatrix[, 5]==4 & oldmatrix[, 6] == 1, 2, drop=FALSE]

If you just want a subset of column 2 as a vector, you can leave off the drop=FALSE part.

Reading "An Introduction to R" should have save you some trouble in the first place.

Andy
 
> thx in advance
> 
> matthias
> 	[[alternative HTML version deleted]]
> 
> 


------------------------------------------------------------------------------
Notice:  This e-mail message, together with any attachments,...{{dropped}}