All,
I want to store a Mata scalar in my Stata data set using st_store(), but
only in certain cases, as determined by selectvar. My reading of the
st_data() help file (where st_store() directs you to concerning
selectvar) says that the following should work:
clear
cap mata: mata drop myfunc()
set obs 1
gen double rc = .
gen double x = .
mata
function myfunc(x, a) return(x^2 - a)
a = 2
rc = (mm_root(x = .,&myfunc(),0,1,0,1000,a)==0)
st_store(1,"rc",rc)
st_store(1,"x",1,x)
end
list
My Stata variable "rc" is equal to one if the mm_root() function has
found a valid solution. I only want st_store() to write the solution to
the data set when it is valid.
Instead, the program correctly writes the solution to the data set when
it is valid (try by changing a to "a = 2/3" above) but generates a
"3200 conformability error" when it is invalid (try the program as
written above, which generates no valid solution because it looks
between 0 and 1 for the square root of 2).
Maybe this is a simple error in my reading of how to use selectvar but I
have tried it by placing "rc" and, alternatively, by placing 1 (the
variable number of "rc") in the third argument of st_store(). Both ways
give the same conformability error.
Any thoughts would be appreciated. Thanks in advance,
Bob
--
------------------------------------------------------------------------
Bob Hammond
Department of Economics
North Carolina State University
Office: (919) 513-2871
Fax: (919) 515-7873
http://www4.ncsu.edu/~rghammon/
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