How do i type mean bias error (mbe) for arrays X i, Y i in matlab

For i= 1:365;
N= 365
 Err= (1/N)*(summation ((Xi)-(Yi)));

I dont think the 'summation' is correct

Answer 1

[ahmed elmanawy]

Err= (1/N)*(sum((Xi)-(Yi)));

[Fatma HM]

what's mean Xi,Yi ?