[R] indexing matrices with dimnames?

[Thomas Lumley]

On 7 Aug 2002, Michael A. Miller wrote:

> I've got a covariance matrix that I'd like to index using the
> dimnames:
>
> > vcov1
>               n0            x0             s            n1            n2
> n0   82.43824759  1.839505e-02 -4.975196e-01  2.882394e+03 -2.615986e-01
> x0    0.01839505  6.134010e-03 -7.695922e-04 -6.373946e+01  6.086321e-03
> s    -0.49751964 -7.695922e-04  9.638943e-03  3.406594e+02 -3.173671e-02
> n1 2882.39407745 -6.373946e+01  3.406594e+02  1.036195e+08 -9.361243e+03
> n2   -0.26159863  6.086321e-03 -3.173671e-02 -9.361243e+03  8.506608e-01
>
> I'd like to select particular elements by name, rather than
> numeric index.  For example, vcov1[1,1] returns 82.43824759.  Is
> there a way to use the dimnames to extract the n0,n0 element?
>

The obvious thing to try is  vcov1["n0","n0"], which works.

	-thomas

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