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I am using the functions in the R survey-library, and per this example on Stackoverflow, I use bquote() and as.name() to dynamically construct the formula for specifying the variables.

This works fine for svytable(), but not for svychisq(). For example:

library(survey)

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

colvar <- 'sch.wide'
rowvar <- 'awards' 

svytable(bquote(~.(as.name(rowvar)) + .(as.name(colvar)) ), dstrat)

      sch.wide
awards      No     Yes
   No  1065.69 1170.74
   Yes    0.00 3957.57

svychisq(bquote(~.(as.name(rowvar)) + .(as.name(colvar)) ), dstrat)

Error in terms.default(formula) : no terms component nor attribute

Can I make this dynamic variable-specification more robust, so that svychisq() picks up the correct terms?

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mhermans
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1 Answers1

4

It looks like svychisq doesn't evaluate it's first parameter in the same way that svydesign does. The bquote is returning a language object that's not being evaluated into a proper formula. You can call the eval yourself to overcome that issue.

svychisq(eval(bquote(~.(as.name(rowvar)) + .(as.name(colvar)) )), dstrat)
#         Pearson's X^2: Rao & Scott adjustment
# 
# data:  svychisq(eval(bquote(~.(as.name(rowvar)) + .(as.name(colvar)))),     dstrat)
# F = 77.2769, ndf = 1, ddf = 197, p-value = 7.364e-16

you could also consider building the formula as a string

svychisq(as.formula(paste("~", rowvar, "+", colvar)), dstrat)
MrFlick
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  • Thank you for the second option. I was just to about to post a "competing answer", since I thought it was more intuitive. – IRTFM Nov 13 '14 at 20:58