svycontrast {survey} R Documentation

## Linear and nonlinearconstrasts of survey statistics

### Description

Computes linear or nonlinear contrasts of estimates produced by survey functions (or any object with coef and vcov methods).

### Usage

svycontrast(stat, contrasts, add=FALSE, ...)


### Arguments

 stat object of class svrepstat or svystat contrasts A vector or list of vectors of coefficients, or a call or list of calls add keep all the coefficients of the input in the output? ... For future expansion

### Details

If contrasts is a list, the element names are used as names for the returned statistics.

If an element of contrasts is shorter than coef(stat) and has names, the names are used to match up the vectors and the remaining elements of contrasts are assumed to be zero. If the names are not legal variable names (eg 0.1) they must be quoted (eg "0.1")

If contrasts is a "call" or list of "call"s, and stat is a svrepstat object including replicates, the replicates are transformed and used to compute the variance. If stat is a svystat object or a svrepstat object without replicates, the delta-method is used to compute variances, and the calls must use only functions that deriv knows how to differentiate. If the names are not legal variable names they must be quoted with backticks (eg 0.1).

### Value

Object of class svrepstat or svystat

regTermTest, svyglm

### Examples

data(api)
dclus1<-svydesign(id=~dnum, weights=~pw, data=apiclus1, fpc=~fpc)

a <- svytotal(~api00+enroll+api99, dclus1)
svycontrast(a, list(avg=c(0.5,0,0.5), diff=c(1,0,-1)))
## if contrast vectors have names, zeroes may be omitted
svycontrast(a, list(avg=c(api00=0.5,api99=0.5), diff=c(api00=1,api99=-1)))

## nonlinear contrasts
svycontrast(a, quote(api00/api99))
svyratio(~api00, ~api99, dclus1)

## Example: standardised skewness coefficient
moments<-svymean(~I(api00^3)+I(api00^2)+I(api00), dclus1)
svycontrast(moments,
quote((I(api00^3)-3*I(api00^2)*I(api00)+ 3*I(api00)*I(api00)^2-I(api00)^3)/
(I(api00^2)-I(api00)^2)^1.5))

## Example: geometric means
## using delta method
meanlogs <- svymean(~log(api00)+log(api99), dclus1)
svycontrast(meanlogs,
list(api00=quote(exp(log(api00))), api99=quote(exp(log(api99)))))

## using delta method
rclus1<-as.svrepdesign(dclus1)
meanlogs <- svymean(~log(api00)+log(api99), rclus1)
svycontrast(meanlogs,
list(api00=quote(exp(log(api00))),
api99=quote(exp(log(api99)))))

## why is add=TRUE useful?

(totals<-svyby(~enroll,~stype,design=dclus1,svytotal,covmat=TRUE))

svycontrast(totals1, list(quote(E/total), quote(H/total), quote(M/total)))

list(api00=quote(exp(log(api00))), api99=quote(exp(log(api99)))))