This is what I get:
. clear
. set obs 9
obs was 0, now 9
. gen id =_n
. set seed 1234
. gen latitude = uniform()/2
. gen longitude = uniform()/2
.
. mata
------------------------------------------------- mata (type end to
exit) --------------------------------------------------
: X= st_data(.,( "latitude" , "longitude"))
: X =X*(pi()/180)
: dist = J(rows(X),rows(X), 0)
: for (i = 1; i <=rows(X); i++) {
for (j = 1; j <=rows(X); j++) {
dist[i,j] = (1/1.609)*6372.795*(2*asin(sqrt( sin((X[i,1] ///
- X[j,1])/2)^2 + cos(X[i,1])*cos(X[j,1])*sin((X[i,2] ///
- X[j,2])/2)^2 )))
}
}
: N = mm_cond(dist :<= J(rows(dist), cols(dist), 10), ///
J(rows(dist), cols(dist),1), J(rows(dist), cols(dist), 0))
<istmt>: 3499 mm_cond() not found
r(3499);
: st_matrix("N", N)
<istmt>: 3499 N not found
r(3499);
: dist
[symmetric]
1 2 3 4
5 6 7 8
+-----------------------------------------------------------------------------------------------------------------
1 | 0
2 | 5.157033248 0
3 | 21.21062478 21.71534226 0
4 | 26.95060264 27.64838102 5.939930861 0
5 | 16.1570544 21.1565295 30.29833499 34.5960745 0
6 | 14.73674249 19.76346139 22.78331973 26.58113711
8.439103366 0
7 | 6.614080612 9.633040063 15.1934957 20.70923619
17.14313644 12.30209368 0
8 | 22.069818 20.34155009 9.309128607 12.92307095
35.0470512 28.79024435 18.03555849 0
9 | 20.67616548 20.42184227 3.226163273 8.078752624
31.37740006 24.32651125 15.24958295 6.116268222
+-----------------------------------------------------------------------------------------------------------------
9
---------------+
9 0 |
---------------+
: end
----------------------------------------------------------------------------------------------------------------------------
. svmat N
matrix N not found
r(111);
end of do-file
r(111);
.
There are two 3499 errors and two 111s.
So I need to store my unitids (actually school ipeds codes) so that I
can eventually collapse that data on census 2000 info to investigate
what postsecondary schools and types of schools serve what
populations. If I take distances from school to all tracts within,
say, 10 miles, I want to collapse population demographics and create
some descriptives using stata. I can do this the other way around,
too, using tracts as the center of my radii. I can get a return on
the one nearest school, but can't seem to get the next nearest on out
to the edge of the specified radius.
Diego
--------------------------------------------
David Diego Torres
Quoting Scott Merryman <[email protected]>:
Sorry - I forgot to mention the code uses Ben Jann's -moremata-.
What is the error?
The example returns the distance matrix and neighbor matrix and then
creates the N variables in the original data set:
: dist
[symmetric]
1 2 3 4
5 6 7 8 9
+--------------------------------------------------------------------------------------------------------------------------------+
1 | 0
|
2 | 5.157033248 0
|
3 | 21.21062478 21.71534226 0
|
4 | 26.95060264 27.64838102 5.939930861 0
|
5 | 16.1570544 21.1565295 30.29833499 34.5960745
0 |
6 | 14.73674249 19.76346139 22.78331973 26.58113711
8.439103366 0 |
7 | 6.614080612 9.633040063 15.1934957 20.70923619
17.14313644 12.30209368 0 |
8 | 22.069818 20.34155009 9.309128607 12.92307095
35.0470512 28.79024435 18.03555849 0 |
9 | 20.67616548 20.42184227 3.226163273 8.078752624
31.37740006 24.32651125 15.24958295 6.116268222 0 |
+--------------------------------------------------------------------------------------------------------------------------------+
+-----------------------------------------------------------------------+
| id latitude longit~e N1 N2 N3 N4 N5 N6 N7
N8 N9 |
|-----------------------------------------------------------------------|
1. | 1 .23851 .0647102 1 1 0 0 0 0 1
0 0 |
2. | 2 .1653217 .0502572 1 1 0 0 0 0 1
0 0 |
3. | 3 .1722953 .3643155 0 0 1 1 0 0 0
1 1 |
4. | 4 .1788673 .4499913 0 0 1 1 0 0 0
0 1 |
5. | 5 .4713051 .043847 0 0 0 0 1 1 0
0 0 |
|-----------------------------------------------------------------------|
6. | 6 .4298635 .1586816 0 0 0 0 1 1 0
0 0 |
7. | 7 .251903 .1594484 1 1 0 0 0 0 1
0 0 |
8. | 8 .0454795 .3190092 0 0 1 0 0 0 0
1 1 |
9. | 9 .1304665 .3436173 0 0 1 1 0 0 0
1 1 |
+-----------------------------------------------------------------------+
Why do you want to store the neighboring unit ids?
Scott
On Sun, Aug 30, 2009 at 10:40 AM, David Torres<[email protected]> wrote:
I copied and pasted your example, Scott, and got a couple of error messages
about N matrix not found. I installed the moremata files, but this didn't
solve the problem. I'm not quite as adept at using stata as some, so,
please, bear with me. I've never used a mata command, so would like to know
whether its use will allow for variable creation wheere the unitids can be
stored and reshaped and all that jazz?
Thanks,
--------------------------------------------
David Diego Torres, MA(Sociology)
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