You can't use the equality operator == with doubles. See Floating-Point Numbers for details. Instead you need to use a tolerance check when comparing. So something like
find(abs(range - 67.2) < 0.00001)
In the above, we look at the absolute difference between the elements of the range array and 67.2. If that difference is less than some tolerance, then we consider the two numbers to be "close enough" to each other.
