[R] Quantiles on multiply imputed survey data - mitools

[Anthony Damico]

is the `with` not passing make.formula( get( 'var_name' ) ) through to
svyquantile for some reason?  does this work?

MIcombine( with(des, svyquantile(~LBXTCD, .5)))


if that's not it, could you make a minimal reproducible example that
includes the data download?  code to download and import nhanes here

https://github.com/ajdamico/asdfree/tree/master/National%20Health%20and%20Nutrition%20Examination%20Survey



On Tue, May 10, 2016 at 4:33 PM, Anne Bichteler <
abichteler at toxstrategies.com> wrote:

> Hello, and thank you for considering this question:
>
> The svystat object created with multiply imputed NHANES data files is
> failing on calling survey::svyquantile. I'm wondering if I'm diagnosing the
> issue correctly, whether the behavior is expected, and whether y'all might
> have any ideas for workarounds.
>
> I'm following T. Lumley's general method outlined here:
> http://faculty.washington.edu/tlumley/old-survey/svymi.html, but with
> data files I've imputed myself on the 2001/2002 biennial. Each file has
> 1081 observations and no missing values.
>
> ### Create the survey design object with list of imputed data files
> ImputedList0102.
> des <- svydesign(id=~SDMVPSU, strat=~SDMVSTRA, weight=~WTSPO2YR,
> data=imputationList(ImputedList0102), nest=TRUE)
>
>
> ### Blood analyte of interest
> var_name <- "LBXTCD" # analyte in blood serum
>
> ### All is well calculating the mean:
> M <- with(des, svymean(make.formula(get('var_name'))))
> summary(M)
> Result <- MIcombine(M)
> Result$coefficients
> # LBXTCD
> # 17.41635
>
>
> ### but svystat object fails to calculate a 50th percentile:
> ### it fails when hard-coding the name rather than using make.formula;
> ### it fails regardless of number of files or choices in handling ties or
> interval type.
> ### There are 16 ties in each data file.
> M1 <- with(des, svyquantile(make.formula(get('var_name')), quantiles =
> c(.5)))
> summary(M1)
>
> #     Length Class  Mode
> #[1,] 1      -none- numeric
> #[2,] 1      -none- numeric
> #[3,] 1      -none- numeric
>
>
> ### The quantile is successfully calculated on one file at a time,
> however, and is different for each file.
> ### (had thought perhaps there was a lack-of-variance issue). The quantile
> calculated on each file
> ### is the same regardless of interval.type.
> des_single1 <- svydesign(id=~SDMVPSU, strat=~SDMVSTRA, weight=~WTSPO2YR,
> data=ImputedList0102[[1]], nest=TRUE)
> svyquantile(make.formula(get('var_name')), des_single1, c(.5))
> # 0.5
> # LBXTCD 13.5554
>
>
> des_single2 <- svydesign(id=~SDMVPSU, strat=~SDMVSTRA, weight=~WTSPO2YR,
> data=ImputedList0102[[2]], nest=TRUE)
> svyquantile(make.formula(get('var_name')), des_single2, c(.5))
> # 0.5
> # LBXTCD 14.06154
>
> # The number of observations exceeding the 50th percentile differs for
> each file, which I can't claim to understand.
>
> # I removed the 16 ties, but no help. Do the ties and/or different number
> of observations above/below prevent the svydesigns from being combined?
> nrow(subset(ImputedList0102[[1]], LBXTCD > 13.5554))
> # [1] 516
> nrow(subset(ImputedList0102[[2]], LBXTCD > 14.06154))
> # [1] 512
>
>
> I'm hoping someone can point me to some gross error I'm making or another
> function parameter or data manipulation or another survey-savvy method
> altogether to calculate a 50th percentile across multiply imputed data
> files. Thanks for any advice,
>
> Brennan
>
> www.toxstrategies.com
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