st: extract part of matrix e(b)

[Mirko <mirko.moro@gmail.com>]

Dear Statalisters,

I wish to extract only some coefficients from the matrix e(b) and I
wonder how this can be achieved.

Here is a simple example.

. regress mpg foreign i.rep78##c.weight headroom
(output omitted)

. margins, dydx(rep78)
(output omitted)

. mat b =e(b)

This command extracts and saves the entire coefficients matrix e(b) as b.

If you type:

. mat li b

you get:

b[1,5]
            1b.          2.          3.          4.          5.
         rep78       rep78       rep78       rep78       rep78
y1           0   .25956254  -.74363551  -.38630819  -6.5437415


What should I do if I wish to grab only the second and third
coefficients:  .25956254,  -.74363551 instead the all matrix?

How this can be done?

Mirko
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