a sequence of a sum of product

I have a sequence H and a function (erfc).

I want to find a sequence of a sum of product such that

H=[1 2 3 4 5 6 7 8 9 0]

for p =(1:10)

h(p) = H(m)*erfc(p-m+1) where m goes from 1 to p

that means

h(1) = H(1)* erfc(1)

h(2) = H(1)*erfc(2)+ H(2)* erfc (1)

h(3) = H(1)*erfc(3) + H(2)*erfc(2)+H(3)*erfc(1)

h(4) = H(1)*erfc(4)+H(2)*erfc(3)+H(3)*erfc(2)+H(4)*erfc(1)

and so on

My biggest hurdle is to indexing sequence H so that I can multiply with the function. I am getting error related to sym/subsindexing.

Any help is greatly appreciated.

Thank you Maharjan

[Andrew Newell]

Can you show us the code you have so far?

[Maharjan]

Thanks Andrew for you interest. So far, I got

    syms m p
    for i=(1:1:N) % N is length of a sequence
    k=(p-m+1);
    q= erfc(k);
    h=symsum(q,m,1,p);
    f=symfun(h,p);
    a(i)=f(i);
    b(i)=eval(a(i));
    end

This gives me exactly what I wanted to get before multiplying by H (listed above). Theoretically, I just need to multiply q by H ("q*H(m)") and replace q by the new term in "h". But I could not structured my codes so that Matlab knows what I wanted to do. I get an error related to a subsindex.

Thank you

Answer 1

[Roger Stafford]

You can vectorize your summation. I assume H is a 10-element row vector as you have shown it.

   h = zeros(10,1);
   for p = 1:10
     h(p) = H(1:p)*erfc((p:-1:1)');
   end

Note: You could also use matlab's 'conv' (convolution) function.

[Maharjan]

I did not realize that i was doing convolution until you mentioned. Thanks for your help. I truly needed the break through. I was convoluted with in symbolic math.

[Wasim Abbas]

could you please send me your code. I need this in my research