On Mon, 26 Jan 2004 20:15:51 +0100, <[EMAIL PROTECTED]> wrote:

I want to conditionally operate on certain elements of a matrix, let me
explain it with a simple vector example


z<- c(1, 2, 3)
zz <- c(0,0,0)
null <- (z > 2) & ( zz <- z)
zz
[1] 1 2 3

why zz is not (0, 0, 3) ?????
<snip>

in the other hand, it curious that null has reasonable values


null
[1] FALSE FALSE TRUE

What you have done there is create a boolean vector, null, of the same length as z (and zz).


For instance:
(z > 2) & (zz <- z)
=(F F T) & (T T T) (as assignment - presumably - returns T)
=(F F T).

What will work is:
z <- c(1, 2, 3)
index <- z>2
zz <- z * index


-- SC

Simon Cullen
Room 3030
Dept. Of Economics
Trinity College Dublin

Ph. (608)3477
Email [EMAIL PROTECTED]

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