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Looping with -qreg- [was: Re: st: Thread-Index: AczWnG9bfd8mYxtIRa2sdn3BOpo1xA==]

 From Nick Cox To statalist@hsphsun2.harvard.edu Subject Looping with -qreg- [was: Re: st: Thread-Index: AczWnG9bfd8mYxtIRa2sdn3BOpo1xA==] Date Thu, 19 Jan 2012 11:45:45 +0000

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There are problems at various levels with your code.

1. The line

local `b' = scalar(u99)

looks like a mistake. If local b _was_ previously defined, then you
need to refer to what this line defines as ``b''.

2. But you don't refer either to `b' or to ``b'' after defining it, so
all you have done is defined something but never used it.

3. If local b was not previously defined, this line would not work.
But that is not what you are reporting, so my guess is that a "local
b" is defined earlier in your code.

4. If you have a scalar, there is no obvious need to put it into a
local for what you want to do.

5. I don't understand what you want to do, but you are changing
results, not instructions. Later runs of -qreg- pay no attention to
e(b) produced by earlier runs of -qreg-.

6. -matrix b- and -local b- are completely different entities.

Nick

On Thu, Jan 19, 2012 at 11:21 AM, STANEVA A. (497186)
<A.V.STANEVA.497186@swansea.ac.uk> wrote:

> Can someone help me with this loop in a qreg?
> This first line works ok!
>
> forval i = 1/99 {
>  local q = `i'/100
>  quietly qreg \$y \$x if public==0, quantile(`q') nolog
>  matrix b = e(b)
>  matrix b[1, colnumb(b,"_cons")] = scalar(u99) /*I get the constant and replace it with the scalar u99, that I want/
> }
>
> The problem comes here. I want the replaced u99 to be included in my qreg and then to get the predictions based on that regression:
>
> forval i = 1/99 {
>  local q = `i'/100
>  local `b’= scalar (u99)
>  quietly qreg \$y \$x if public==0, quantile (`q') nolog
>  predict xb if public==0
>  preserve
>  keep if xb~=.
>  restore
>  }
> However, there is a problem in the line local`b'=scalar(u99), it seems stata doesn’t replace the _cons with the u99. It runs normal qreg, ignoring all this manipulations.
>

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