R help - Aug 2007 - alternate methods to perform a calculation

Consider a data frame (x) with 2 variables, x1 and x2, having equal values. 
It looks like:

x1   x2
1    1
2    2
3    3

Now, consider a second data frame (xk):
xk1   xk2
0.5    0.5
1.0    0.5
1.5    0.5
2.0    0.5
0.5    1
1.0    1
1.5    1
2.0    1
0.5    1.5
1.0    1.5
1.5    1.5
2.0    1.5
0.5    2
1.0    2
1.5    2
2.0    2

I have written code to calculate some differences between these two data
sets; the main idea is to subtract off each element of xk1 from each value
of x1, and similarly for xk2 and x2.  This is what I have:

w1 <- array(NA,dim=c(nrow(xk),length(x$x1)))
w2 <- array(NA,dim=c(nrow(xk),length(x$x2))) 
for (j in 1:nrow(xk)) {
	w1[j,] <- abs(x$x1-xk$xk1[j])
	w2[j,] <- abs(x$x2-xk$xk2[j])
}

Is there  a way to do the above calculation without use of a FOR loop? 
Thank you

Derek


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I think you can use 'outer'

outer(b$xk1, a$x1, function(y,z)abs(z-y))
outer(b$xk2, a$x2, function(y,z)abs(z-y))

On 8/28/07, dxc13 <dxc13 at health.state.ny.us>
wrote:
>
> Consider a data frame (x) with 2 variables, x1 and x2, having equal values.
> It looks like:
>
> x1   x2
> 1    1
> 2    2
> 3    3
>
> Now, consider a second data frame (xk):
> xk1   xk2
> 0.5    0.5
> 1.0    0.5
> 1.5    0.5
> 2.0    0.5
> 0.5    1
> 1.0    1
> 1.5    1
> 2.0    1
> 0.5    1.5
> 1.0    1.5
> 1.5    1.5
> 2.0    1.5
> 0.5    2
> 1.0    2
> 1.5    2
> 2.0    2
>
> I have written code to calculate some differences between these two data
> sets; the main idea is to subtract off each element of xk1 from each value
> of x1, and similarly for xk2 and x2.  This is what I have:
>
> w1 <- array(NA,dim=c(nrow(xk),length(x$x1)))
> w2 <- array(NA,dim=c(nrow(xk),length(x$x2)))
> for (j in 1:nrow(xk)) {
>        w1[j,] <- abs(x$x1-xk$xk1[j])
>        w2[j,] <- abs(x$x2-xk$xk2[j])
> }
>
> Is there  a way to do the above calculation without use of a FOR loop?
> Thank you
>
> Derek
>
>
> --
> View this message in context:
http://www.nabble.com/alternate-methods-to-perform-a-calculation-tf4344469.html#a12376906
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?