Coalesce.R: A coalesce function for R (returns first non-NA value from a list of vectors)

coalesce.R

coalesce<-function(...) {
    x<-lapply(list(...), function(z) {if (is.factor(z)) as.character(z) else z})
    m<-is.na(x[[1]])
    i<-2
    while(any(m) & i<=length(x)) {
        if ( length(x[[i]])==length(x[[1]])) {
            x[[1]][m]<-x[[i]][m]
        } else if (length(x[[i]])==1) {
            x[[1]][m]<-x[[i]]
        } else {
            stop(paste("length mismatch in argument",i," - found:", length( x[[i]] ),"expected:",length( x[[1]] ) ))
        }
        m<-is.na(x[[1]])
        
        
# Usage
x<-c(1,NA,NA,4,5)
y<-c(NA,22,NA,44,NA)
z<-c(100,200,300,400,500)

coalesce(x,y)
coalesce(x,y,-1)
coalesce(x,y,z)
        i<-i+1
    }
    return(x[[1]])
}