issue in find variable

[Muhammad Usman Gul]

Please explain to me why it gives me an empty matrix? Out of 100 only following 25 thresholds are also gives empty matrix

0.0600, 0.0700, 0.1000, 0.1500, 0.1800, 0.2100, 0.2400, 0.2900, 0.3500, 0.3600, 0.4100, 0.4200, 0.4700, 0.4800, 0.5700, 0.5800, 0.6900, 0.7000, 0.7100, 0.8200, 0.8300, 0.8400, 0.9400, 0.9500, 0.9600

[Stephen23]

"Please explain to me why it gives me an empty matrix?"

Read about the behaviors of 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

http://faculty.tarleton.edu/agapie/documents/cs_343_arch/papers/1991_Goldberg_FloatingPoint.pdf

Answer 1

[Fangjun Jiang]

floating point data precision issue. Below is an example, a and b are not equal even though all the visible digits are the same.

>> format long
>> a=1-1/3
a =
   0.666666666666667
>> b=2/3
b =
   0.666666666666667
>> a==b
ans =
  logical
   0
>> abs(a-b)<=eps
ans =
  logical
   1

[Muhammad Usman Gul]

Actually, I have a column matrix that contains different numbers between 0.001 to 1. For example, the 0.0600 value is repeated 7 times in the matrix. I would like to find out these numbers along with their indexes. I am trying to use for loop to find out where is exact number occurring. As I am facing above issue, anyone can suggest be how to extract the desire value from the matrix?

[Fangjun Jiang]

find(abs(YouData-0.06)<=eps)

[Muhammad Usman Gul]

Its work, Thanks all of you