[R] apply( )

[Chuck Cleland]

Greg Tarpinian wrote:
> I have a question that must have a simple answer (but eludes me).
> I need a row-by-row logical comparison across three numeric variables
> in
> a data frame: foo$x, foo$y, foo$z.  The logic is
> 
>    if( x < y || x > z ) 1 else 0
> 
> for a particular row.
> 
> It is simple and very inefficient to use for(i in 1:length(foo$x)){ }
> loops.  How can I accomplish this using sappy( ) / lapply( ) / apply( )
> or some other more efficient method?

X <- as.data.frame(matrix(rnorm(30), ncol=3))
X
            V1         V2         V3
1  -0.48026236  0.8629789 -1.2600858
2  -1.32408219 -0.5590268  1.1310638
3   0.02717575 -0.5661402  0.7824019
4   0.80783373  0.2300440 -0.4477275
5   1.24518907 -0.3778392  1.7546530
6  -0.39254125 -1.0388962 -0.4436296
7  -1.44473455  1.8606963  0.4253889
8  -0.63543047 -1.6408418 -1.0409473
9   0.81075970  0.3914066 -1.0361739
10  1.66021280 -1.6694101 -0.4810839

with(X, ifelse(V1 < V2 | V1 > V3, 1, 0))
 [1] 1 1 0 1 0 1 1 1 1 1

> Thank you in advance,
> 
>     Greg
> 
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-- 
Chuck Cleland, Ph.D.
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