# [R] Package corpcor: Putting symmetric matrix entries in vector

Steven Yen syen04 at gmail.com
Sat Jan 31 01:34:49 CET 2015

```Great! Thanks. Thanks to all who tried to help.
as.vector(r[upper.tri(r)]) does it:

> e<-as.matrix(cbind(u1,u2,u3,v1,v2,v3))
> r<-cor(e); r
[,1]       [,2]        [,3]        [,4]       [,5]        [,6]
[1,]  1.00000000  0.5240809  0.47996616  0.11200672 -0.1751103 -0.09276455
[2,]  0.52408090  1.0000000  0.54135982 -0.15985028 -0.2627738 -0.14184545
[3,]  0.47996616  0.5413598  1.00000000 -0.06823105 -0.2046897 -0.23815967
[4,]  0.11200672 -0.1598503 -0.06823105  1.00000000  0.2211311  0.08977677
[5,] -0.17511026 -0.2627738 -0.20468966  0.22113112  1.0000000  0.23567235
[6,] -0.09276455 -0.1418455 -0.23815967  0.08977677  0.2356724  1.00000000
> as.vector(r[upper.tri(r)])
[1]  0.52408090  0.47996616  0.54135982  0.11200672 -0.15985028 -0.06823105
[7] -0.17511026 -0.26277383 -0.20468966  0.22113112 -0.09276455 -0.14184545
[13] -0.23815967  0.08977677  0.23567235

At 06:56 PM 1/30/2015, Peter Langfelder wrote:
>If you have a symmetric matrix, you can work with the upper triangle
>instead of the lower one, and you get what you want by simply using
>
>as.vector(A[upper.tri(A)])
>
>Example:
>
> > a = matrix(rnorm(16), 4, 4)
> > A = a + t(a)
> > A
>            [,1]      [,2]       [,3]        [,4]
>[1,]  0.3341294 0.5460334 -0.4388050  1.09415343
>[2,]  0.5460334 0.1595501  0.3907721  0.24021833
>[3,] -0.4388050 0.3907721 -0.4024922 -1.62140865
>[4,]  1.0941534 0.2402183 -1.6214086  0.03987924
> > as.vector(A[upper.tri(A)])
>[1]  0.5460334 -0.4388050  0.3907721  1.0941534  0.2402183 -1.6214086
>
>No need to play with potentially error-prone index vectors; upper.tri
>does that for you.
>
>Hope this helps,
>
>Peter
>
>On Fri, Jan 30, 2015 at 3:03 PM, Steven Yen <syen04 at gmail.com> wrote:
> > Dear
> > I use sm2vec from package corpcor to puts the lower triagonal entries of a
> > symmetric matrix (matrix A) into a vector. However, sm2vec goes downward
> > (columnwise, vector B), but I would like it to go across (rowwise). So I
> > define a vector to re-map the vector (vector C). This works. But is there a
> > short-cut (simpler way)? Thank you.
> >
> >> A<-cor(e); A
> >             [,1]       [,2]        [,3]        [,4]       [,5]        [,6]
> > [1,]  1.00000000  0.5240809  0.47996616  0.11200672 -0.1751103 -0.09276455
> > [2,]  0.52408090  1.0000000  0.54135982 -0.15985028 -0.2627738 -0.14184545
> > [3,]  0.47996616  0.5413598  1.00000000 -0.06823105 -0.2046897 -0.23815967
> > [4,]  0.11200672 -0.1598503 -0.06823105  1.00000000  0.2211311  0.08977677
> > [5,] -0.17511026 -0.2627738 -0.20468966  0.22113112  1.0000000  0.23567235
> > [6,] -0.09276455 -0.1418455 -0.23815967  0.08977677  0.2356724  1.00000000
> >> B<-sm2vec(A); B
> >  [1]  0.52408090  0.47996616  0.11200672 -0.17511026 -0.09276455
> >  [6]  0.54135982 -0.15985028 -0.26277383 -0.14184545 -0.06823105
> > [11] -0.20468966 -0.23815967  0.22113112  0.08977677  0.23567235
> >> jj<-c(1,2,6,3,7,10,4,8,11,13,5,9,12,14,15)
> >> C<-B[jj]; C
> >  [1]  0.52408090  0.47996616  0.54135982  0.11200672 -0.15985028
> >  [6] -0.06823105 -0.17511026 -0.26277383 -0.20468966  0.22113112
> > [11] -0.09276455 -0.14184545 -0.23815967  0.08977677  0.23567235
> >
> > ______________________________________________
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```