find(vector==value) not working
조회 수: 22 (최근 30일)
이전 댓글 표시
Why does find(vector==value) not work? I am trying to find the index of a value of 0.16 in a vector defined as vector=0:0.01:0.3. find(vector==0.16) should return 17 but returns an empty vector. Why?
댓글 수: 0
채택된 답변
Star Strider
2019년 11월 13일
You have encountered floating-point approximation error. See the documentation on Floating-Point Numbers for a full explanation.
Try this:
vector=0:0.01:0.3;
Result = find(vector<=0.16, 1, 'last');
producing:
Result =
17
댓글 수: 0
추가 답변 (2개)
Ruger28
2019년 11월 13일
From the FIND documentation
To find a noninteger value, use a tolerance value based on your data. Otherwise, the result is sometimes an empty matrix due to floating-point roundoff error.
y = 0:0.1:1
y = 1×11
0 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000 0.8000 0.9000 1.0000
k = find(y==0.3)
k = 1x0 empty double row vector
k = find(abs(y-0.3) < 0.001)
k = 4
댓글 수: 0
Thomas Satterly
2019년 11월 13일
While it looks like the 17th value of your vector is 0.16, it's actually slightly off because of floating point precision. What you should do is find the closest value to your target value that's below an acceptable limit. For example:
vector = 0:0.01:0.3;
tolerance = eps * 2; % eps is the floating point number tolerance
target = 0.16;
match = find(abs(vector - target) <= tolerance);
댓글 수: 0
참고 항목
카테고리
Help Center 및 File Exchange에서 Matrices and Arrays에 대해 자세히 알아보기
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!