Sum of even numbers

this is what i was trying

function s = test(n)

if n <= 0 %for n<= 0 the result would be 0

s = 0;

elseif % if n is a decimal (positiv or neg. ) the result would be Nan

n ~= floor(n)

s=Nan; %not a number

else

sum(2:2:n) % Example( test(4) = 2+4=6, or test(6)=2+4+6=12)

end

it does not work, has anybody a suggestion ?

Answer 1

[Alan Stevens]

Like so

s = test(6);
disp(s)

    12

function s = test(n)
    if n <= 0 %for n<= 0 the result would be 0 
        s = 0;
    elseif n ~= floor(n) % if n is a decimal (positiv or neg. ) the result would be Nan
     s=NaN; %not a number
    else    
        s = sum(2:2:n); % Example( test(4) = 2+4=6, or test(6)=2+4+6=12)
    end
end

Answer 2

[Kartikay Sapra]

function s = even_sum(n)
    if n <= 0
        s = 0
    else if n~=floor(n)
        s = NaN
    else
        s = sum(2:2:n)
    end
end

Few suggestions:

1. Nan is undefined, one should use NaN: Not a Number
2. function name 'test' might clash with an inbuit function.
3. In else condition, assign sum(2:2:n) to s