Notice: On March 31, it was announced that Statalist is moving from an email list to a forum. The old list will shut down on April 23, and its replacement, statalist.org is already up and running.

# st: mata programming - input type

 From Tomáš Houška To statalist@hsphsun2.harvard.edu Subject st: mata programming - input type Date Wed, 20 Mar 2013 23:16:41 +0100

```Dear Stata list,

I am trying to write this loop (here I give an example in "stata
language", but I am aware that this will never work as mata cannot be
processed within Stata loop):

Example:

levelsof time_period, local(period_id)

foreach period of local period_id {
mata
//import STATA matrices
EPSILON = st_matrix("EPSILON_M`period'")
PRICE   = st_matrix("PRICE_M`period'")
SHARE   = st_matrix("SHARE_M`period'")

BETA = EPSILON :* ( (SHARE *(1:/PRICE)') )

st_matrix("BETA`period'",BETA)

end
}

Which means I have several matrices, each marked by period number and
I am trying to perform some operations on them (here I give a
simplified example of my code). I would like to create a mata function
that would take "period_id" as an input (period_id is always in
integer) and process the mata code, resulting in creating new matrix
BETA`period_id'.

So far I have been able to come up with this:
Example 2:

mata
mata clear
void mc_estim(string scalar period) {
//import STATA matrices
EPSILON = st_matrix("EPSILON_M`period'")
PRICE   = st_matrix("PRICE_M`period'")
SHARE   = st_matrix("SHARE_M`period'")

BETA = EPSILON :* ( (SHARE *(1:/PRICE)') )

st_matrix("BETA`period'",BETA)
}
end
* run mata function with a selected input
mata mc_estim(534)

But I am not sure how to use the "input" in the mata function code (I
expect that the notation is different from Statas local macros....) I
would appreciate any help on this.
Thank you!
T.
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/faqs/resources/statalist-faq/
*   http://www.ats.ucla.edu/stat/stata/
```