Make subset dataset in mata space but I could not find any help about it.

[ha lee]

Dear all.

I'm trying to make subset dataset in mata space but I could not find any help about it.

for example..

If I have a list of variables of (year x1 x2 x3) and I would like to make subset matrix by "year".

So if year==1990, I would like to make matrix "mat" with all the variables which is in 1990.

mata:
st_view(xx=.,.,("year","x1",x2","x3"))

if (xx[.,1]==1990) {

mat=xx[.,.]

}

The code presented above doesn't work.

Does anybody can help me??

Thanks a lot.

[Christophe Kolodziejczyk]

ha lee the if condition should be a scalar. Then

x[.,.]

returns the whole matrix

There are two solutions

1. use select() or st_select (see the help for more details)
2. use st_view with a predefined variable selecting the right year. This variable is passed to st_view() as an additional argument

The first solution is most probably the one you want

mat = select(xx,xx[,1]:==1990) // note the use of the colon operator for doing element by element operations

or

st_select(mat,xx,xx[:,1]:==1990)

In this case since xx is a view, mat will also be a view.

Another way is to directly specify mat with st_view(). Mat will be a view.

gen d1990 = year == 1990
// the third argument select all the rows from your variables where d1990 is different from 0
mata: st_view(mat=.,"year x1 x2 x3","d1990" )

[ha lee]

Thank you Christophe .