Some clarificatins of anova() and summary ()

anyone please explain why this happens.. I know this happens when x1
and x2 has different sizes. but here x1 and x2 have same dimension.

Given that this is a homework problem, I think the onus is on you to
figure this out, not on us to help you.  In almost all classes, you
are expected to work on homework by yourself, and not solicit help
from others - this is often known as "cheating".

Hadley

http://had.co.nz/