Dear list.
Courtesy of Kerry Kamirre,
Here is the answer to my previous posting.
Mata is really great.
I'd like to thank both Nick Cox and Kerry.
Have a wonderful weekend.
Amadou.
----- Forwarded by Amadou Bassirou Diallo/Person/World Bank on 11/11/2005 02:43
PM -----
tech-support
Sent by:
[email protected] To
[email protected]
cc
11/11/2005
12:36 PM Subject
Re: Minimum of a vector or a matrix.
Dear Amadou,
There isn't any looping needed to perform these calculations. This can all be
done using the ":" operators. Here is an example of the syntax:
--begin log--
: A = (0,2,3\1,2,3\3,1,5)
: B = colmin(A)\colmin(A)\colmin(A)
: C = B:==A
: C
1 2 3
+-------------+
1 | 1 0 1 |
2 | 0 0 1 |
3 | 0 1 0 |
+-------------+
: B = rowmin(A),rowmin(A),rowmin(A)
: D = B:==A
: D
1 2 3
+-------------+
1 | 1 0 0 |
2 | 1 0 0 |
3 | 0 1 0 |
+-------------+
: E = C:&D
: E
1 2 3
+-------------+
1 | 1 0 0 |
2 | 0 0 0 |
3 | 0 1 0 |
+-------------+
--end of log--
Sincerely,
Kerry Kammire
************************************************************************
___ ____ ____ ____ ____ tm
/__ / ____/ / ____/
___/ / /___/ / /___/ Kerry Kammire
Statistics/Data Analysis Technical Services
[email protected]
StataCorp LP
4905 Lakeway Drive
College Station, TX 77845
"VISIT OUR WEB SITE" http://www.stata.com
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************************************************************************
You wrote:
-----Begin Original Message-----
Hi,
I've checked with the statalist but I need a rather urgent answer
to this question.
Nick Cox pointed me in a direction but I cannot take from there
and get to the final solution.
Here is my question.
Suppose you have a matrix:
: A
1 2 3
+-------------+
1 | 0 2 3 |
2 | 1 2 3 |
3 | 3 1 5 |
+-------------+
I want a true condition being placed on each element of the 3 columns.
Element is one 1 if it is the smallest value of the column, and 0 otherwise.
So I want:
+-------------+
1 | 1 0 1 |
2 | 0 0 1 |
3 | 0 1 0 |
+-------------+
My other question is:
Element (i,j) is 1 if it is the smallest value of the column j AND the column i
, and 0 otherwise.
I want:
+-------------+
1 | 1 0 0 |
2 | 0 0 0 |
3 | 0 1 0 |
+-------------+
Here is what I coded, but I do not know how to implement double loops in mata.
clear
cap mata clear
mata:
A = (0,2,3\1,2,3\3,1,5)
r = cols(A)
A
r
B = colmin(A)\colmin(A)\colmin(A)
B
J = J(r,r,0)
J
for (i=1;i<=r;++i {
J[i,j] = cond([A[i,j]==colmin(A),1,0)
}
J
Best regards.
Amadou.
-----End Original Message-----
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