Running a sum function using a for loop?

I am running the following script: function[x]=sum1 (x,a,b)

total=0;

For k=1:length(x)

    if a <=x(k)<=b
      total=total+x (k);

    end

end

y=total

end

On the command window i state

b= 4 14 6 3 4 10 8 6

y1=sum1(b,-5,0)

Ans=0

y2=sum1 (b,1,3)

Ans=55

I don't understand how this is obtain. I would think the answer is 3. Because what I'm trying to do is to add the number of b that fall between 1 and 3.

Answer 1

[bio lim]

function[x]=sum1 (x,a,b)
total=0;

 for k=1:length(x)
    if x(k) >= a & b >= x(k)
     total = total + x(k);
    end
 end

 y = total

 end

You can't write if a <=x(k)<=b. You must use the & expression.

Answer 2

[Jan]

a <= x(k) <= b is evaluated from the left to the right:

1. a <= x(k) : This is either true or false, which is treated as 1 or 0
2. 1 <= b or 0 <= b

This is not what you want. As posted already use the & operator or better &&.

By the way: You do not need a loop. This is nicer and faster:

total = sum(x(a <=x & x<=b));