sum(c*b,'a​ll')>sum(c​)*sum(b)

b=[0.4 0.4 0.1 0.1]
c=[0.6 0.4]'
sum(c*b,'all')>sum(c)*sum(b) 

returns 1.

sum(c)=sum(b)=1, while sum(c*b,'all') seems to be larger than 1. Why is that?

Answer 1

[Matt J]

Floating point discrepancies. You cannot count on floating point calculations giving a perfectly accurate result of 1 (unless they involve only integer arithmetic).

>> x=c*b;  sum(x(:))-1

ans =

     2.220446049250313e-16

[Gergely Bunth]

Thank you. Now I remember I should have known this.