[R] "Survey" package and NAMCS data... unsure of specification

From: David L. Van Brunt, Ph.D. <dlvanbrunt_at_gmail.com>
Date: Wed 05 Oct 2005 - 07:44:27 EST

Hello, all.

I wanted to use the "survey" package to analyze data from the National Ambulatory Medical Care Survey, and am having some difficulty translating the analysis keywords from one package (Stata) to the other (R). The data were collected using a multistage probability sampling, and there are variables included to identify the sampling units and weights. Documentation from the NAMCS describes this for Stata as follows (note the variable names in the data are in caps):

The pweight (PATWT), strata (CSTRATM), and PSU (CPSUM) are set with the svyset command as
svyset pweight PATWT
svyset strata CSTRATM
svyset psu CPSUM

They provide similar instructions for SUDAAN: as SUDAAN 1-stage WR Option
The program below provides a with replacement ultimate cluster (1-stage) estimate of standard errors for a
PROC CROSSTAB DATA=COMB1 DESIGN=WR FILETYPE=SAS; NEST CSTRATM CPSUM/MISSUNIT; In R, the svydesign command is used to set the sampling scheme, but as follows (example from the documentation):

dstrat <- svydesign(id=~1,strata=~stype, weights=~pw, data=apistrat, fpc=~fpc)

 stratified on stype, with sampling weights pw. The fpc variable contains the population size for the stratum. As the schools are sampled independently, each record in the data frame is a separate PSU. This is indicated by id=~1. Since the sampling weights could have been determined from the population size an equivalent declaration would be

dstrat <- svydesign(id=~1,strata=~stype, data=apistrat, fpc=~fpc)

I get that the "weights" should be PATWT, and it seems that the "strata" should be CSTRATM, but I'm unsure of how to handle the primary sampling units (CPSUM).

Does anyone have any suggestions?


David L. Van Brunt, Ph.D.

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