Finite-Sum Function

Hello All,

I would like to create a function S_N, that would return the Nth term of a series. Here's what I have so far:

 1 function S_N = S(N)
 2 k = 1:N 
 3 A_k = 1./(k.^(3/2)+k.^(1/2))
 4 S_N = cumsum(A_k)
 5 end

MatLab politely replies:

>> S_N
Error using S_N (line 2)
Not enough input arguments.

I'm not sure what else MatLab wants. I would think this is a pretty simple fix for this uber program. (I can do it perfectly on my TI89 :D)

Much Thanks, Jim

Answer 1

[Andrew Newell]

S_N is the output, but the function name is S. Use, e.g.,

S(10)

(you'll need to input a number).

Answer 2

[Jan]

You've defined S_N such that it needs one input argument. So call it like:

S_N(3)

Answer 3

[Atom]

Much thanks;

At the bottom is my final code for anyone else that would want to know. (Of course! I have to give him a number). By the way, the infinite sum is referred to as "Theodorus' constant". It seems pretty hard to approx. Here are the first fifty digits:

1:86002 50792 21190 30718 06959 15717 14332 46665 24121 52345...

function S_N = S(N) 
k = 1:N; 
A_k = 1./(k.^(3/2)+k.^(1/2)); 
S_N = sum(A_k) 
end

[Andrew Newell]

I did a quick search on Theodorus constant, and all the sources said it is the square root of 3, or 1.73205 ...

[Radu Trimbitas]

There are two Theodorus constant, square root of 3 and sum of the series sum_{n=1}^{\infty} \frac{1}{k^{3/2}+k^{1/2}} ....