Hello all
I have what seems like a simple question but have not been able to find an
answer on the forum. I'm trying to define a function which involves
regression models and a large number of covariates.
I would like the function to accept any number of covariates and, ideally, I
would like to be able to enter the covariates in a group (e.g. as a list)
rather than individually. Is there any way of doing this?
Example:
#define function involving regression model with several covariates
custom <- function(outcome, exposure, covar1, covar2, covar3){
model <- lm(outcome ~ exposure + covar1 + covar2 + covar3)
expected <- predict(model)
summary(expected)
}
library(MASS)
attach(birthwt)
custom(bwt, lwt, low, age, race) #Works when 3 covariates are specified
custom(bwt,lwt,low,age) # Does not work with < or > 3 covariates
varlist <- list(low,age,race)
custom(bwt,lwt, varlist) #Does not work if covariates are included as a list
Thanks very much for your help
Tim
--
Tim Elwell-Sutton
University of Hong Kong
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