Re: st: Allocating values from a matrix to a new variable in Stata

[Nick Winter <nw53@cornell.edu>]

Assuming you have the distance matrix in a Stata matrix called "D", then 
this should do it:

. generate distance = D[x,y]

(I am assuming that the diagonal of the distance matrix contains zeros, so 
there is no need to deal with x==y as a separate step.

If you have missing values for either x and/or y, you might need to modify:

. generate distance = D[x,y] if !missing(x) & !missing(y)

--Nick WInter


At 01:41 PM 5/3/2005 -0400, you wrote:

> Hi,
>
> I'm using Intercooled Stata 8, and am not an experienced user.
> It will be great if someone can help me out with this.
>
> I have a dataset where I have about 18,000 records each having a value for X
> and another for Y that ranges from 1 to 32.
> I have another 32*32 matrix that gives the distances between all X and Y
> pairs.
>
> Whenever a record has X=Y, I want to introduce a new variable distance =
> zero.
> Otherwise, I want to assign distance = the appropriate distance value for
> (X,Y) from this matrix I have.
>
> For example, if X=1 and Y=1, distance = 0.
> If X=1 and Y=2, distance = 25 (value obtained from the distance matrix)
> If X=2 and Y=1, distance = 25 (same as above)
> If X =1 and Y=3, distance = 15 ...... And so on.
>
> Can someone please suggest the most efficient way to do this in Stata?
>
> Many thanks,
> Anjali
>
> ------------------------------
> Anjali Mahendra
> Doctoral student
> Department of Urban Studies and Planning
> Massachusetts Institute of Technology
> ------------------------------
>
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