compute triple summation for my homework

hello guys

I have need to compute the following summation for my homework. Any hint or pseudo code would be helpful. Thanks.

Edit - "p" is a vector containing numbers and p(x) refers to the element position in that vector and "y" is a symbol

[androidguy]

using wolfram i got something like this -

https://www.wolframalpha.com/input/?i=(sum(sum(p(x)+*+y(x,t)%5Em)+m+from+1+to+3,+x+from+0+to+2,+t+from+1+to+3))

Answer 1

[Walter Roberson]

Since y is a symbol, you will need to use the Symbolic Toolbox.

You might be tempted to use symsum() for this, but symsum has the limitation that symbolic variables cannot be used for indexing of arrays.

So... ndgrid, calculate the formula for each point, and then sum() along the dimensions until you get a scalar result.

[androidguy]

Thanks for the hint sir. I will try this and ask further.

[androidguy]

i done this and i get error - "Subscript indices must either be real positive integers or logical."

syms s
P = [12 10 8];
[t,x,m] = ndgrid(1:3, 0:2, 1:3);
Z(t,x) = s.^m
Z1 = P(x)
Z2 = Z .* Z1
final = sum(z2)

[Steven Lord]

There's no such thing as element 0 in a MATLAB array. MATLAB indexing starts at 1, but you're trying to work with P(0).

[androidguy]

My teacher said that it is okay to start the second summation from 1 instead of 0. Also how do i assign variables for each varying index? For example when x=1 and t=1, i need a variable like y11 and when x=2 and t=2 y22 and so on. How can i do this?

[Walter Roberson]

y = sym('y', [3, 2]);
y(t, x)

Answer 2

[androidguy]

can anyone help me on this one please? i would really appreciate it