RE: [R] Best way to store negative indexes

From: Liaw, Andy <andy_liaw_at_merck.com>
Date: Wed 28 Jul 2004 - 11:53:23 EST


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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>



R-help@stat.math.ethz.ch mailing list
https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed Jul 28 12:01:58 2004

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