how does sum work?

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Pavel Kuzmitsky
Pavel Kuzmitsky 2020-11-22
编辑： Walter Roberson 2020-11-23
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

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采纳的回答

Walter Roberson
Walter Roberson 2020-11-23
you have one / operator that should be ./
  3 个评论
显示 1更早的评论
James Tursa
James Tursa 2020-11-23
(((-1).^(s)).*(factorial(n-(s))))/... <-- that one
Walter Roberson
Walter Roberson 2020-11-23
编辑：Walter Roberson 2020-11-23
Ran in:
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');

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