如何在 R 中应用与 NIS（国家住院患者样本）相关的权重

Question

I am trying to apply weights given with NIS data using the R package "survey", but I have been unsuccessful. I am fairly new to R and survey commands.

This is what I have tried:

# Create the unweighted dataset
d <- read.dta13(path) 

# This produces the correct weighted amount of cases I need.
sum(d$DISCWT) # This produces the correct weighted amount of cases I need.

library(survey)

# Create survey object
dsvy <- svydesign(id = ~ d$HOSP_NIS, strata = ~ d$NIS_STRATUM, weights = ~ d$DISCWT, nest = TRUE, data = d) 
d$count <- 1
svytotal(~d$count, dsvy)

However I get the following error after running the survey total:

Error in onestrat(x[index, , drop = FALSE], clusters[index], nPSU[index][1],  : 
 Stratum (1131) has only one PSU at stage 1

Any help would be greatly appreciated, thank you!

Answer 1

The error indicates that you have specified a design where one of the strata has just a single primary sampling unit. It's not possible to get an unbiased estimate of variance for a design like that: the contribution of stratum 1131 will end up as 0/0.

As you see, R's default response is to give an error, because a reasonably likely explanation is that the data or the svydesign statement is wrong. Sometimes, as here, that's not what you want, and the global option 'survey.lonely.psu' describes other ways to respond. You want to set

options(survey.lonely.psu = "adjust")

This and other options are documented at help(surveyoptions)