Matrix Calculation

[Peter Vaughn]

Good morning,

I'm calculating with matrices and am building new matrices out of old ones, which shouldn't be an issue. However, the following is not accepted by Stata, returning an r(132) error (brackets/parenthesis error):

matrix VWNOR = (
EVNOR[1,1] / (EVNOR[1,1] + EVNOR[1,2]) \
EVNOR[1,2] / (EVNOR[1,1] + EVNOR[1,2]))

Where EVNOR is the following matrix:


EVNOR[1,5]
Eigenvalues: Eigenvalues: Eigenvalues: Eigenvalues: Eigenvalues:
Comp1 Comp2 Comp3 Comp4 Comp5
r1 3.7321743 .94771372 .26798242 .05102239 .00110712


The above calcs should be working since [1,1-5] are all scalars, right? What's the issue? Thanks a lot for your inputs.

Best,

Peter

[Nick Cox]

It is easier to get into Mata to do this. Stata's matrix language does not support many complicated expressions.

. matrix EVNOR = (3.7321743, .94771372, .26798242, .05102239, .00110712)

. mata
------------------------------------------------- mata (type end to exit) --------------------------------
: EVNOR = st_matrix("EVNOR")

: VWNOR = (EVNOR[1,1] / (EVNOR[1,1] + EVNOR[1,2]) \ EVNOR[1,2] / (EVNOR[1,1] + EVNOR[1,2]))

: VWNOR
                 1
    +---------------+
  1 |  .7974922229  |
  2 |  .2025077771  |
    +---------------+

: vwnor = EVNOR[1..2]' :/ rowsum(EVNOR[1..2])

: vwnor
                 1
    +---------------+
  1 |  .7974922229  |
  2 |  .2025077771  |
    +---------------+

[Peter Vaughn]

Great, thanks Nick. But how can I now save VWNOR as a matrix in regular Stata. I can display it in Mata but

matrix list VWNOR

in regular Stata does not display it....

Thanks!

[Peter Vaughn]

Ok, I got it. Same command, other way around. Thanks