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Re: st: Generating a vector


From   "Gauri Khanna" <gwkhanna@hotmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Generating a vector
Date   Sun, 21 May 2006 17:02:19 +0000

Dear Phil,

I have resent my message with subject line "generating a matrix, adding values in a column"

I experimented with the following that you suggested


. mat a = J(1,5,23)

. mat li a
which produced the value 23 in all 5 columns

Instead I would like to generate 326 rows with say 3 columns with each column having a different value repeated 326 times.

c1 c2 c3
r1 10 22 53
r2 10 22 53
r3 10 22 53
r4 10 22 53

Is there any way whereby these columns can be given a name?

Regards,

Gauri

From: Phil Schumm <pschumm@uchicago.edu>
Reply-To: statalist@hsphsun2.harvard.edu
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: Generating a vector
Date: Sat, 20 May 2006 16:08:26 -0500

On May 20, 2006, at 1:07 AM, Gauri Khanna wrote:
I would like to generate an 1 x n vector, (n=326 rows) for cross sectional data. This is actually an input price vector.

I would then want to fill it with three or four input prices that I have computed elsewhere. Hence the same value for each of the inputs will be repeated 326 times.

I don't understand; if the vector is 1 x 326, and if each value will be repeated 326 times, then you'll need 4 separate vectors to hold the 4 values, no?



I guess the first step would be to generate an empty(?)/null vector and then fill it with values for each of the inputs.

I'm sorry, but there's really not enough here to give much of an answer. If you want to generate a matrix containing a constant value, then you want to use the function J(), like so:


. mat a = J(1,5,23)

. mat li a

a[1,5]
c1 c2 c3 c4 c5
r1 23 23 23 23 23


Note that -help matrix- (followed by clicking on "matrix functions") would have also given you this answer. So, the first "meta-answer" to your question is really a suggestion that if you want to work with matrices in Stata, you should spend some time with [P] matrix.

In addition, it looks as though your immediate question is just the first step in what is really a larger problem you are trying to tackle. If this is true, then it is really better to ask "I'm trying to do X and I think Y is a good place to start, but I'm having problems" rather than just asking "I can't figure out how to do Y". There are at least two reasons for this. First, Y may not be the best way to start, so you should give people on the list an opportunity to tell you that; after all, getting you started on the right path is half the battle. Second, if you are having problems with Y, there's a good chance you will also have problems with subsequent steps, and it's a lot more efficient for everyone involved if you just give your whole problem up front and let people help you with the entire thing. Moreover, this makes for much more useful list archives (i.e., those who come along later with the same problem will be able to find the answer in a single posting or two, instead of spread across many).

That said, your question suggests that you are working on a economic problem, and not being an economist, I'm afraid others may need to help you solve it (but I too will read their answers and learn). I apologize to the economists on the list for having volunteered your services ;)


-- Phil

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