Can you give a simple example of what you are trying to do?
Would the following help?
> x <- sample(10)
> diffMat <- outer(x, x, "-")
> x
[1] 1 10 5 8 9 6 3 2 4 7
> diffMat
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] 0 -9 -4 -7 -8 -5 -2 -1 -3 -6
[2,] 9 0 5 2 1 4 7 8 6 3
[3,] 4 -5 0 -3 -4 -1 2 3 1 -2
[4,] 7 -2 3 0 -1 2 5 6 4 1
[5,] 8 -1 4 1 0 3 6 7 5 2
[6,] 5 -4 1 -2 -3 0 3 4 2 -1
[7,] 2 -7 -2 -5 -6 -3 0 1 -1 -4
[8,] 1 -8 -3 -6 -7 -4 -1 0 -2 -5
[9,] 3 -6 -1 -4 -5 -2 1 2 0 -3
[10,] 6 -3 2 -1 -2 1 4 5 3 0
> diffTab <- table(diffMat[lower.tri(diffMat, diag=FALSE)])
> diffTab
-8 -7 -6 -5 -4 -3 -2 -1 1 2 3 4 5 6 7 8 9
1 2 3 3 3 4 5 4 5 3 3 3 2 1 1 1 1
> diffTab <- table(abs(diffMat[lower.tri(diffMat, diag=FALSE)]))
> diffTab
1 2 3 4 5 6 7 8 9
9 8 7 6 5 4 3 2 1
Andy
> From: StephaneDemurget
>
> Hi,
>
> I'm trying to figure out how to properly construct a graph of
> frequencies of a difference between 2 values, that is | i | - | j |.
> I'd like to know the best way to store the actual data
> because of course
> doing my_vector[i -j] will not work because the index could
> be negative.
>
> I know there's no hash table so what's the best solution,
> simplicity-wise ? Use a list of pair of values {index, i - j}
> ? Or can I
> somehow use negative index, perhaps using 0array ? Any help would be
> appreciated :)
>
> ATM, I use as.character (i-j) to index my data, but I lose all the
> processing power of R there after.
>
> Sorry If it's written somewhere, but I read a lot of docs about it,
> searched through the ML archives and didn't manage to find an answer.
>
> Please also answer me back at my email address as I am not
> subscribed to
> the list.
>
> Best regards,
>
> --Stephane
>
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