Error code when trying to put mata matrix back into Stata

[Alex Davenport]

Hi
Apologies if this is basic, I'm new to using mata and nothing from previous questions seems to work.
I needed to switch into mata to use the eigensystem command and am now trying to return a single column matrix with 255 rows back into stata.

I brought my data into mata with " w_tilde_mat = st_matrix("w_tilde") "
I used " eigensystem(w_tilde_mat, v_vect_tilde=.,w_val_tilde=.) " to get a 255x255 matrix of 255, 255 row eigenvectors.
I then used " col_ec = w_vect_tilde[.,2] " to extract the second eigenvector which is what I need.

I then want to put col_ec back into stata, and am trying to use st_matrix again, and have tried various things but nothing works.
For example st_matrix("col_ec", col_st_ec) returns an error code with col_st_ec not being found (3499) but this is what I want the matrix created back in stata to be called.

Thanks in advance.

[Andrew Musau]

mata
M =J(5,6,7)
st_matrix("StataM", M[1..., 2])
end
mat l StataM

Res.:

. mat l StataM

StataM[5,1]
    c1
r1   7
r2   7
r3   7
r4   7
r5   7

See

help matrix extraction

I then want to put col_ec back into stata, and am trying to use st_matrix again, and have tried various things but nothing works. For example st_matrix("col_ec", col_st_ec) returns an error code with col_st_ec not being found (3499)

In your case, the error message is meaningful as there is no matrix named "col_st_ec" defined. This should work:

st_matrix("col_st_ec", col_ec)

where the Stata matrix will be named "col_st_ec".