[R] predict.lm(...,type="terms") question

[jjthaden]

The error is generated in the last line of code shown here from predict.lm

> predict.lm
function (object, newdata, se.fit = FALSE, scale = NULL, df = Inf, 
    interval = c("none", "confidence", "prediction"), level = 0.95, 
    type = c("response", "terms"), terms = NULL, na.action = na.pass, 
    pred.var = res.var/weights, weights = 1, ...) 
{
    tt <- terms(object)
    if (!inherits(object, "lm")) 
        warning("calling predict.lm(<fake-lm-object>) ...")
    if (missing(newdata) || is.null(newdata)) {
        mm <- X <- model.matrix(object)
        mmDone <- TRUE
        offset <- object$offset
    }
    else {
        Terms <- delete.response(tt)
        m <- model.frame(Terms, newdata, na.action = na.action, 
            xlev = object$xlevels)
#MORE LINES DELETED HERE...

As written, if newdata is specified but it doesn't contain every term  in
the original data frame, then an error is thrown. But for predict.lm to
predict values for a term, i.e., type = "term", those terms cannot be in the
newdata vector. 
-John



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