What's wrong with my code? (Beginner's question; geometric sum)
显示 更早的评论
This is the sum I'm trying to use:
1 + r^2 + r^4 + r^6 + ... + r^n
If n isn't even, I'm supposed to display an error.
Here's my code:
function [sum] = series(r,n)
sum = 1;
if mod(n,2) == 0
for i=2:n
sum = sum + r.^i;
end
else
disp('Error!');
end
end
Keeps returning the wrong value. What's wrong with my code?
采纳的回答
Roger Stafford
2014-11-13
编辑：Roger Stafford
2014-11-13
Replace
for i=2:n
by
for i=2:2:n
Or you could always just write
(1-r^(n+2))/1-r^2)
for even n.
2 个评论
n
2014-11-13
Image Analyst
2014-11-13
Here is the question Roger answered so people will know after n deletes his question, which he has a bad habit of doing:
This is the sum I'm trying to use:
1 + r^2 + r^4 + r^6 + ... + r^n
If n isn't even, I'm supposed to display an error.
Here's my code:
function [sum] = series(r,n)
sum = 1;
if mod(n,2) == 0
for i=2:n
sum = sum + r.^i;
end
else
disp('Error!');
end
end
Keeps returning the wrong value. What's wrong with my code?
更多回答（1 个）
Image Analyst
2014-11-13
Don't use sum as the name of a variable since it's a built-in function. You want
for k = 2 : 2 : n
theSum = theSum + r^k;
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