Issues using Summation in Matlab

Hi, just want to confirm whether the code that I have below is indeed correct or there are changes that is needed to solve. I have values of "n' and "d" that I have to input but the summation tool id new to me

syms i n d

SMD = symsum(n*d^3/(n*d^2),i,1,N)

formula:

Answer 1

[Chunru]

This is symbolic computation. It's not clear what you want to calculate exactly.

If you have value of d and n, you may want to do numerical summation. For example

d = [1 3 4 2];
n = [2 5 6 7];

% sum first, then division
s1 = sum(d)/(sum(n))

s1 = 0.5000

% division first, then sum
s2 = sum(d./n)

s2 = 2.0524

[Matthew Charles]

Thanks @Chunru duly noted. I will make the necessary adjustments

Answer 2

[Walter Roberson]

never use symsum to form the sum of a vector of values. The variable of summation for symsum is always symbolic, but symbolic values can never be used to index anything.

symsum should only be used when you are working with formulas, such as

symsum((-1)^n / 2^n, n, 1, m)

hoping to get out a function like (-1/2)^m/3 - 1/3

[Matthew Charles]

Okay not a problem, thank you very much