find the position of a value in a "Double-precision array"

Hi, I have a 12904*1 double-precision array in matlab and would like to find the position of a value. For example, when I input "-10.1333", it returns "1", when I input "-10", it returns "5". I tried "find(time_samp==-10.1333)", it just returens "0×1 empty double column vector". Need some help, thank you.

[Stephen23]

This is a completely expected result with binary floating point numbers:

https://www.mathworks.com/matlabcentral/answers/57444-faq-why-is-0-3-0-2-0-1-not-equal-to-zero

https://www.mathworks.com/matlabcentral/answers/316889-why-two-equal-numbers-are-not-equal

http://www.mathworks.com/matlabcentral/answers/102419-how-do-i-determine-if-the-error-in-my-answer-is-the-result-of-round-off-error-or-a-bug

http://www.mathworks.com/matlabcentral/answers/140656-about-numerical-difficulty-of-equality-comparison-operation-between-two-double-real-numbers-in-matlab

This is worth reading as well:

https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html

Instead of incorrectly assuming exact equivalence of binary floating point numbers, compare the absolute difference against a tolerance:

tol = 1e-10; % you select this to suit your data
idx = abs(A-B)<tol;

Answer 1

[John D'Errico]

-10.1333 the EXACT VALUE? NO. All you see is that number written with 4 digits after the decimal point. You need to learn to use a tolerance.

Seriously, is 0.3333 the exact value of 1/3? Of course not! In fact, there is no finite number of digits that will exactly represent that fraction, as a DECIMAL, or as a number stored in a binary form, as it is internally in MATLAB.