Stata The Stata listserver
[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

st: RE: Goodness of fit of -intreg depvar1 depvar2 indepvars, het(subset_of_indepvars) robust-


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Goodness of fit of -intreg depvar1 depvar2 indepvars, het(subset_of_indepvars) robust-
Date   Mon, 12 Apr 2004 18:21:27 +0100

I am probably missing something here, but why not use

predict pred if e(sample)

and then calculate its variance directly? 

Nick 
n.j.cox@durham.ac.uk 

Renzo Comolli
> 
> I would like to have measures of goodness of fit for 
> intreg  depvar1 depvar2 indepvars, het(subset_of_indepvars) robust
> constraints(1)
> 
> The measure I would really like is variance of predicted y, 
> but I would
> settle for other measures too.
> 
> I can't use -fitstat- because it was written for the Stata 7 
> version of
> -intreg-.
> I hacked the code of -fitstat- enough to make it work for 
> Stata 8 version of
> -intereg-, but it does not work if I specify the option -, 
> het()- and I
> don't understand the code enough to hack it further. 
> (I wrote to Mr. Long months ago, so that is not an option)
> 
> I post here my hacked version of the code to compute variance 
> of predicted
> y, but fails (as said) if the -, het()- option is specified.
> 
> capture program drop vystar
> program define vystar, rclass
>     version 6.0
> 
>     tempname n_obs n_parm  b v_ystar v v_y v_x v_e factor bnocon 
> 
>     mat `b' = get(_b)
>     local depv `e(depvar)'
> 
> *-> get information from last model estimated
>     mat `v_e' = J(1,1,1)
>     sca `n_obs' = e(N)
> 
> *-> compute numbers of variables and parameters
>     sca  `n_parm' = colsof(`b')
>     local n_rhs = `n_parm' - 2  /*  for var(e) */ 
>  
>     local varlist : colnames(`b')
>     parse "`varlist'", parse (" ")
> 
>     * 2/11/00
>     * to deal with rhsnam gt 80 characters, can't use string functions
>     local rhsnam ""
>     local i 1
>     while "``i''"!= "" {
>             if "``i''"!="_cons" & "``i''"!="_se" { local 
> rhsnam "`rhsnam'
> ``i''" }
>             local i = `i' + 1
>     }
> 
> *-> compute Var(y*) using cov_x
> 
>         scalar `factor' = 1/(`n_obs'-1)
>         quietly mat accum `v_x' = `depv' `rhsnam' if 
> e(sample), deviations
> noconstant
>         scalar `v_y' = `factor' * `v_x'[1,1] /* sum y/(n-1) */
>         mat `v_x' = `factor' * `v_x'[2...,2...]  /* cov 
> matrix of rhs vars
> */
>         mat `v_x' = `v_x'[2...,2...] 
>         mat `bnocon' = `b'[1,1..`n_rhs'] /* trim off _con */
>         mat `v' = `bnocon' * `v_x' * `bnocon''
>         mat `v_e'[1,1] = e(sigma)*e(sigma) 
>         mat `v' = `v' + `v_e'
>         scalar `v_ystar' = `v'[1,1]
> 	display "Variance of Fitted y* :" " " `v_ystar'
> 	return scalar v_ystar = `v_ystar'
> 
> end


*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index