Message-ID: <ea57975b050829144536b9cf43@mail.gmail.com>
Date: 2005-08-29T21:45:41Z
From: Shengzhe Wu
Subject: Help: predict.qda
Hello,
I use the function qda (package MASS) to obtain a qda object like below.
x.qda = qda(x, group)
the group is a factor of two levels
and use this object to do the prediction below.
y.pred = predict(x.qda, y)
after that, I set different prediction priors like below, but the
results of prediction are totally the same as above using prior of
training set (use all.equal to compare).
y.pred1 = predict(x.qda,y, prior = c(1, 0))
y.pred2 = predict(x.qda,y, prior = c(0.5, 0.5))
y.pred3 = predict(x.qda,y, prior = c(0, 1))
y.pred4 = predict(x.qda,y, prior = c(0, 0))
the prediction prior of the last one should be wrong, but I still got
the same result.
And I tested the example of the function predict.qda by setting a
prediction prior.
predict(z, test, prior = c(0.1, 0.1, 0.8))
this result is exact the same as "predict(z, test)" which use training prior
"c(0.3333333, 0.3333333, 0.3333333)"
If the prediction prior for qda does not work?
The version of R I use is 2.1.1, and this argument for lda works.
Thank you,
Shengzhe