Title says it all.

x = c(1,2,3)
print(norm(x, type='2')-x%*%x)

Prints: -10.25834

Why are they not equal?

CodePudding user response：

Because the 2-norm is the square root of t(x) %*% x:

> print(norm(x, type='2')^2-x%*%x)
     [,1]
[1,]    0