 |
[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]
Re: st: corr_svy & covariance matrix for survey data
Many thanks for sending along the code, Steve. Can you provide some
explanation for some lines of the code so that I can understand better
what exactly I would be doing to get the matrix?
Specifically, why am I only standardizing the weight variable? Should
I also be standardizing the cluster and stratum variable? What exactly
do the "w" and the "v" in the code to generate the n^2 covariance
terms mean/represent? What would I be doing exactly in the format c_*
%20.5fc line of the code and why does that number change in the code
to get the covariance? (i.e. format c_* %15.5fc)
On Oct 2, 2008, at 1:50 PM, Steven Samuels wrote:
In addition, does anyone know how to use the matrix I am trying to
obtain above to obtain a covariance matrix that can be easily
transferred to Mplus or LISREL for CFA and SEM analyses?
In Stata V 10 Version 10.1 corr_svy does not return the proper
correlation matrix, at least for p>2 dimensions.
The following code should get you the covariance matrix in a list.
I don't know anything about the programs you want to feed into, so
you will have to manipulate the list yourself to suit their
requirements.
********************* CODE BEGINS**********************
* Create covariance matrix for survey data
*******************************************************
sysuse auto,clear
svyset _n [pweight=rep78]
gen wt000=weight/1000 //standardize to avoid large values
********************************************************
* put variables into a macro
*******************************************************
local cvars mpg wt000 trunk
*******************************************************
* Get means
*******************************************************
svy: mean `cvars' //outputs weighted means in _b[varname]
*******************************************************
* Get n^2 covariance terms
*******************************************************
foreach w of varlist `cvars' {
foreach v of varlist `cvars' {
gen c_`w'_`v' = ((`w' - _b[`w'])^2)*((`v' - _b[`v'])^2)
}
}
format c_* %20.5fc
*******************************************************
* Get Covariances
*******************************************************
svy: mean c_*
format c_* %15.5fc
matrix clist = vec(e(b))
matrix list clist
*****************CODE ENDS*************************
On Oct 1, 2008, at 9:57 PM, Ishtar Govia wrote:
Dear List,
I am using Stata 10/SE 10.1 for Macs. I have two questions. One
concerning the --corr_svy-- module and error messages I have been
getting, the second concerning how to obtain a covariance matrix
for complex survey sample data, within Stata.
I am working with a complex survey sample dataset and am using
Stata for some preliminary data analyses (univariate and
multivariate checks for normality, efas) before moving to Mplus for
SEM modeling. I installed the --corr_svy-- module from within Stata
by typing "ssc install corr_svy"
However, in my first attempt below, I got the following error
message:
svy, subpop (if race3cat==2 & sex==1 & (riwyes==1 & riwyes <.)):
corr_svy lesscurt lessresp poorserv notsmart actfraid thkdisho
actbettr callnmes trethara follstor, pw obs sig
corr_svy is not supported by svy with vce(linearized); see help svy
estimation for a list of Stata estimation commands that are
supported by svy
r(322);
I then attempted to reset the weight and design variables, and run
the --corr_svy--, following the example in the "help" for the --
corr_svy--, excluding my subpop specification.
. svyset clust [pweight=wgtcentriw], strata (stratum) ||_n
Note: stage 1 is sampled with replacement; all further stages will
be ignored
pweight: wgtcentriw
VCE: linearized
Single unit: missing
Strata 1: stratum
SU 1: clust
FPC 1: <zero>
. corr_svy lesscurt lessresp poorserv notsmart actfraid thkdisho
actbettr callnmes trethara follstor, pw obs sig
This worked--but it didn't include my subpop specification. I then
tried the same thing with my subpop specifcation and it DIDN'T
work. Any ideas on how to use the corr_svy module to obtain the
correlation matrix, accounting for the weight and design variables
and allowing me to restrict my analyses to my subpop of interest?
corr_svy lesscurt lessresp poorserv notsmart actfraid thkdisho
actbettr callnmes trethara follstor [pweight=wgtcent],
strata(stratum) psu(clust) subpop(if race3cat==2 & sex==1 &
(riwyes==1 & riwyes <.)) pw obs sig print(10) star(5)
subpop() does not contain a valid varname
r(198);
. svyset clust [pweight=wgtcentriw], strata (stratum) ||_n
Note: stage 1 is sampled with replacement; all further stages will
be ignored
pweight: wgtcentriw
VCE: linearized
Single unit: missing
Strata 1: stratum
SU 1: clust
FPC 1: <zero>
. corr_svy lesscurt lessresp poorserv notsmart actfraid thkdisho
actbettr callnmes trethara follstor, pw obs sig
In addition, does anyone know how to use the matrix I am trying to
obtain above to obtain a covariance matrix that can be easily
transferred to Mplus or LISREL for CFA and SEM analyses?
Thanks for your consideration,
Ishtar Govia
[email protected]
*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/