how does sum work?

I don't understand what I'm doing wrong, it should be -1, but it turns out -0.5

but if you calculate separately for s=0 and s=1 and add it up, it turns out that -1 is true

clear
clc
n=2;
m=0;
k=(n-m)/2;
q=(n+m)/2;
r2=0;
s=0:k;
  R=sum((r2.^(n-(2.*(s)))).*...
     (((-1).^(s)).*(factorial(n-(s))))/...
     ((factorial(s)).*(factorial(q-(s))).*(factorial(k-(s)))))

also, if you can explain how to improve the formula so that it can be used when

  r2=linspace(0,1,500);

if you can, write comments on actions in the response so that it is clear how your code works

Answer 1

[Walter Roberson]

you have one / operator that should be ./

[Pavel Kuzmitsky]

I have summation should occur when changing s, r2 is an array, what operators are we talking about?

[James Tursa]

(((-1).^(s)).*(factorial(n-(s))))/...   <-- that one

[Walter Roberson]

n = 6;
m=0;
k=(n-m)/2;
q=(n+m)/2;
r2 = linspace(0,1,25);
s = (0:k).';
R = sum((r2.^(n-(2.*(s)))) .* ...
     (((-1).^(s)).*(factorial(n-(s)))) ./ ...
     ((factorial(s)).*(factorial(q-(s))).*(factorial(k-(s)))));
size(R)

ans = 1×2

1 25

●

plot(r2, R);
xlabel('r2'); ylabel('R');