Why am I getting "Array indices must be positive integers or logical values" error?

Array indices must be positive integers or logical values.

Error in A2Q1>LinearConv (line 68)

yc(i) = yc(i) + x1(i-j+1).*x2(j);

function yfnc = LinearConv(x1, x2, len)
    yc = zeros(1, len);
    for i = 1:len
    %Total terms will be 1 to len
        for j = 1:(i+1)
            if(i-j+1<length(x1) && j<length(x2)) 
                yc(i) = yc(i) + x1(i-j+1).*x2(j); 
                %Equation
            end
        end
    end
yfnc = yc;
end

[Shubh Shah]

Thanks for correcting me, I forgot to change j's iteration from 1 to i

Answer 1

[Stephen23]

Consider this indexing:

x1(i-j+1)

What value does it have on the last iteration of the j loop? (hint: zero).

i-j+1 % that index
j = i+1 % last iteration
i-(i+1)+1 % substitute j
i-i-1+1 % zero