On 14-09-2013, at 18:35, gildororo...@mail-on.us wrote:
> This is better explained by example:
>
>> A <- data.frame(force = sort(runif(10, 0, 1)), condition =
>> sort(sample(0:100, 10)))
>> B <- data.frame(counterforce = sort(runif(15, 0, 1), decreasing=T),
>> condition = sort(sample(0:100, 15)))
>
> So we have:
>
>> A
> force condition
> 1 0.03515542 1
> 2 0.13267882 13
> 3 0.26155689 24
> 4 0.37453142 38
> 5 0.39360520 45 <--- trim everything after this
> 6 0.43924737 48
> 7 0.47669800 50
> 8 0.57044795 51
> 9 0.81177499 61
> 10 0.98860450 94
>
>> B
> counterforce condition
> 1 0.965769548 2
> 2 0.965266255 5
> 3 0.846941244 7
> 4 0.818013029 11
> 5 0.813139978 22
> 6 0.730599939 34
> 7 0.715985436 39
> 8 0.658073895 40
> 9 0.421264948 42 <--- trim everything after this
> 10 0.373774505 52
> 11 0.242191461 62
> 12 0.090584590 63
> 13 0.070020635 68
> 14 0.067366062 83
> 15 0.001585313 84
>
> I need to trim away rows after No. 5, from A, trim away rows after No. 9,
> from B.
>
> Because
>
> A[5, condition] > max(B[1:9, condition] && A[5, force] > B[9+1, counterforce]
>
> In a general way, I am looking for x and y, where:
>
> A[x, condition] > max(B[1:y, condition] && A[x, force] > B[y+1, counterforce]
>
> and I will select A[1:x,] and B[1:y,], or trim away the rest, because they
> are irrelevent for the calculation onwards.
>
> This is easy to do it in C, and I actually have done it in C-like R script,
> by looping through all rows of A, and breaking from the loop when finding the
> matching trim-point in B. But I am learning R, so what is the native way to
> do it in R?
Your trim-point in B is not unique (at least for the data you provided).
Use a loop in R like this
for( x in seq_len(nrow(A)) ) {
for( y in seq_len(nrow(B)-1) ) {
res1 <- A[x,"condition"] > max(B[1:y,"condition"])
res2 <- A[x,"force"] > B[y+1,"counterforce"]
res <- res1 && res2
if(res) cat("x=",x,"y=",y,"res=",res,"\n")
}
}
Result is:
# x= 5 y= 9 res= TRUE
# x= 6 y= 8 res= TRUE
# x= 6 y= 9 res= TRUE
# x= 7 y= 8 res= TRUE
# x= 7 y= 9 res= TRUE
# x= 8 y= 8 res= TRUE
# x= 8 y= 9 res= TRUE
# x= 9 y= 5 res= TRUE
# x= 9 y= 6 res= TRUE
# x= 9 y= 7 res= TRUE
# x= 9 y= 8 res= TRUE
# x= 9 y= 9 res= TRUE
# x= 9 y= 10 res= TRUE
# x= 10 y= 1 res= TRUE
# x= 10 y= 2 res= TRUE
# x= 10 y= 3 res= TRUE
# x= 10 y= 4 res= TRUE
# x= 10 y= 5 res= TRUE
# x= 10 y= 6 res= TRUE
# x= 10 y= 7 res= TRUE
# x= 10 y= 8 res= TRUE
# x= 10 y= 9 res= TRUE
# x= 10 y= 10 res= TRUE
# x= 10 y= 11 res= TRUE
# x= 10 y= 12 res= TRUE
# x= 10 y= 13 res= TRUE
# x= 10 y= 14 res= TRUE
If you want a unique answer you'll need additional restrictions.
Berend
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