matlab double comparison

Question

I am trying to compare an array of doubles to a scalar double for equality, but equality is never recognized under certain circumstances. I suspect that this has to do with

Answer 1

Something is probably in single precision somewhere, and double elsewhere. The binary representation of e.g. 10.2 in each is different as they terminate after a different number of bits. Thus they are different:

>> if (single(10.2) == 10.2) disp('honk'); end
>> if (single(10.2) == single(10.2)) disp('honk'); end
honk

You'll need to check for equality within some small difference:

 eps = 0.001;
 result = abs(array-10.2) < eps;

You can find the precision used in an array using whos:

>> whos A
  Name      Size            Bytes  Class     Attributes

  A         1x2                 8  single