Passing saved matrix name to mata from stata

[Matthew J. Baker]

Dear fellow Mata enthusiasts --

I have the following seemingly simple problem for which I can find no workaround. The problem involves passing a local to Mata from Stata, where the local contains the name of a saved matrix. What I want to do is load up the saved matrix using name contained in the local. For example:

local MatName "SomeMatrix"
mata
     file=st_local("MatName")
     mata matuse file
end

Running the above code gives me the error:

file file.mmat not found
r(601);

So, the problem is I can't get mata to use the contents of file, rather than "file" itself, in the matrix importing command.

Is there any way around this?

All the best,

Matt

[Christophe Kolodziejczyk]

If you're using matuse in interactive mode, you can use directly the local.

local MatName "SomeMatrix"
mata
     mata matuse `MatName'
end

By the way this command is only for interactive use. If you want to do something similar in non-interactive use fgetmatrix()

[Jeff Pitblado (StataCorp)]

You can just use the macro directly in the Mata code.
Here is a silly example that stores a Mata copy of regression coefficients in a
temporary file, clears Mata, then reads the matrix back in.

sysuse auto
regress mpg turn trunk
tempfile bmat
mata: b = st_matrix("e(b)")
mata: b
mata: mata matsave `"`bmat'"' b
mata: mata matdescribe `"`bmat'"'
mata: mata clear
mata: mata d
mata: mata matuse `bmat'
mata: mata d
mata: b

[Matthew J. Baker]

Christophe and Jeff --

Very good! With reference to Christophe's comment, I outsmarted myself by making things harder than they had to be. And Jeff's comment reminded me of the nested quotes - which I never seem to be able to get the hang of!

Thanks,

Matt