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RE: st: mata for-if-else

From   "Nick Cox" <>
To   <>
Subject   RE: st: mata for-if-else
Date   Wed, 14 Apr 2010 11:44:58 +0100

There are several mistakes here. 
The syntax of -for- requires semi-colons. 
Testing for equality requires == not =. 
Mata has no equivalent of Stata's -if- qualifier. 

Positively, this codes more congenially using ?: 


for(i=1; i<1001; i++) {
	a[i]  = b[i] == 1 ? 2 : 3 


Abhimanyu Arora

Thanks Sabrina, but unfortunately the problem persists.

If I understood correctly what you meant, I used the following:



for(i=1,i<1001,i++) {
a[i]=2 if b[i]==1
a[i]=3 if b[i]!=1



Sabrina Carrossa

I am not sure, but I guess you'd better use the "if qualifier" instead
of the "if-else" command.

On 14 April 2010 10:54, Abhimanyu Arora

> I have simplified my problem to a large extent, but essentially has to
> with using for-if-else commands in mata. I would like to create a
> whose values depend on an existing matrix 'b' (both are 1000X1 vectors
> precise). I need to tell mata the dimension of a first. But all I get
> executing the commands below is the original vector 'a'. What could be
> possible error? I have tried adding and removing braces but it is not
> working...
> a=J(1000,1,.)
> for(i=1,i<1001,i++) {
> if (b[i]==1){
> a[i]=2
> }
> else {a[i]=3
> }
> }
> a
> end

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