How can the "find" function fail at finding elements in an array?

Dear all,

I have used many times the "find" function with very good results... until now. Here is my VERY SIMPLE code:

a = [0.145:0.0005:0.175];
index = find(a == 0.16)
 index =

   Empty matrix: 1-by-0

   index2 = find(a == 0.15)

    index2 =

    11

   So...  both numbers (0.15 and 0.16) EXIST in the array named "a", however, ONLY 0.15 IS FOUND... 

I have checked this in R2015a and R2013b with the same results... Does anybody haves an idea of what is going on???

Best regards, Ion

Answer 1

[Star Strider]

You have discovered ‘floating point approximation error’.

See: Why is 0.3 - 0.2 - 0.1 (or similar) not equal to zero? for an explanation.

EDIT —

To illustrate:

a = [0.145:0.0005:0.175];
index = find(a <= 0.16, 1, 'last')
result = a(index)
err = result - 0.16                                 % Floating Point Error

result =
         0.16

err =
  -2.7756e-17