Why are these sums not the same?
조회 수: 1 (최근 30일)
이전 댓글 표시
Hello together,
What is the difference between these two:
1:
>>sum(cos(0.5*pi)*(0:99))
ans =
3.0310e-13
and 2:
>>S=0;
>> for J=0:99
S=cos(0.5*pi)*j;
end;
>> S =
6.0620e-15
Why is there a different result?
Thank you for any help!
댓글 수: 0
채택된 답변
Roger Stafford
2015년 1월 16일
편집: Roger Stafford
2015년 1월 16일
There is no reason they should be the same! In the for-loop method you are not doing a summation, as is done in the first method. All you obtain is the value of the last term, namely cos(0.5*pi)*99.
If you change the last method to
S = S + cos(0.5*pi)*j;
any difference between that value and the one for the first method will be due to differences in round off errors.
Ideally cos(0.5*pi) should be an exact zero, but both because pi cannot be represented exactly and because of errors in the cosine computation, it actually gives 6.1232e-17 as its value.
댓글 수: 0
추가 답변 (1개)
참고 항목
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!