# What's new in the survey package

There’s a new version of the survey package on CRAN (yay!). A lot of it is minor or relatively esoteric fixes. There’s one big change, which will break some people’s code. The svyquantile function has been completely rewritten. You might naively think quantiles are easy, but they aren’t

The $$p$$th quantile is defined as the value where the estimated cumulative distribution function is equal to $$p$$. As with quantiles in unweighted data, this definition only pins down the quantile to an interval between two observations, and a rule is needed to interpolate. As the help for the base R function explains, even before considering sampling weights there are many possible rules (like all the ones base R adopted from Hyndman & Fan’s paper).

As a result of the rewrite, the format of the output is different. If you want the old output, the old function is available as oldsvyquantile. But the new one is better. There’s more information in the qrule vignette.

The svydesign function is much faster for very large data sets with character strings for PSU and stratum identifiers (these got slower when R changed to stringsAsFactors=FALSE).

Another important change is that svyglm handles negative residual degrees of freedom better. The design degrees of freedom for a survey are fairly well defined, but it’s less clear what happens to the residual df in a regression model. Subtracting a degree of freedom for each predictor is conservative (it would be correct if all the predictors were PSU-level). When the predictors are at the individual level it is quite possible to have more predictors than design degrees of freedom, so the residual df are negative. Previously, the summary method just lost it at the idea of negative df; now it gives parameter estimates and standard errors but no $$p$$-values. If you know what residual df you want to use, you can supply it as an argument to summary.

There’s a new convenience function svybys, which does stratified analyses by a list of variables one at a time (rather than jointly, as svyby does)

Also, primarily for teaching, there’s a function poisson_sampling() to set up a design object with Poisson sampling

The complete list of newness is

    svyquantile() has been COMPLETELY REWRITTEN. The old version is available
as oldsvyquantile() (for David Eduardo Jorquera Petersen)

svycontrast()'s improvements for statistics with replicates are now also there with
svyby(), for domain comparisons (Robert Baskin)

svyttest() now gives an error message if the binary group variable isn't binary
(for StackOverflow 60930323)

confint.svyglm Wald-type intervals now correctly label the columns (eg 2.5%, 97.5%)
(for Molly Petersen)

svyolr() using linearisation had the wrong standard errors for intercepts
other than the first, if extracted using vcov (it was correct in summary() output)

svyglm() gave deffs that were too large by a factor of nrow(design). (Adrianne Bradford)

svycoxph() now warns if you try to use frailty or other penalised terms, because they
just come from calling coxph and I have no reason to believe they work correctly
in complex samples (for Claudia Rivera)

coef.svyglm() now has a complete= argument to match coef.default(). (for Thomas Leeper)

summary.svyglm() now gives NA p-values and a warning, rather than Inf standard errors,
when the residual df are zero or negative (for Dan Simpson and Lauren Kennedy)

In the multigroup case, svyranktest() now documents which elements of the 'htest'
object have which parts of the result, because it's a bit weird (for Justin Allen)

svycontrast() gets a new argument add=TRUE to keep the old coefficients as well

twophase() can now take strata= arguments that are character, not just factor
or numeric. (for Pam Shaw)

add reference to Chen & Lumley on tail probabilities for quadratic forms.

add reference to Breslow et al for calibrate()

add svyqqplot and svyqqmath for quantile-quantile plots

SE.svyby would grab confidence interval limits instead of SEs if vartype=c("ci","se").

svylogrank(method="small") was wrong (though method="score" and method="large" are ok),
because of problems in obtaining the at-risk matrix from coxph.detail. (for Zhiwen Yao)

(for Ángel Rodríguez Laso)

logLik.svyglm used to return the deviance and now divides it by -2

svybys() to make multiple tables by separate variables rather than a joint table
(for Hannah Evans)

added predictat= option to svypredmeans for Steven Johnston.

Fixed bug in postStratify.svyrep.design, was reweighting all reps the same (Steven Johnston)

Fix date for Thomas & Rao (1987) (Neil Diamond)

Add svygofchisq() for one-sample chisquared goodness of fit (for Natalie Gallagher)

confint.svyglm(method="Wald") now uses t distribution with design df by default.
(for Ehsan Karim)

confint.svyglm() checks for zero/negative degrees of freedom

confint.svyglm() checks for zero/negative degrees of freedom

mrb bootstrap now doesn't throw an error when there's a single PSU in a stratum
(Steve White)

oldsvyquantile() bug with producing replicate-weight confidence intervals for
multiple quantiles (Ben Schneider)

regTermTest(,method="LRT") didn't work if the survey design object and model were
defined in a function (for Keiran Shao)

svyglm() has clearer error message when the subset= argument contains NAs (for Pam Shaw)
and when the weights contain NAs (for Paige Johnson)

regTermTest was dropping the first term for coxph() models (Adam Elder)

svydesign() is much faster for very large datasets with character ids or strata.

svyglm() now works with na.action=na.exclude (for Terry Therneau)

extractAIC.svylm does the design-based AIC for the two-parameter Gaussian model, so
estimating the variance parameter as well as the regression parameters.
(for Benmei Liu and Barry Graubard)

svydesign(, pps=poisson_sampling()) for Poisson sampling, and ppscov() for
specifying PPS design with weighted or unweighted covariance of sampling indicators
(for Claudia Rivera Rodriguez)