[Python-ideas] Way to check for floating point "closeness"?

[Neil Girdhar]

The problem with this is that if your "actual" is say, 5, then a large
enough "estimate" will always be close.

On Thu, Jan 15, 2015 at 5:06 PM, Ron Adam <ron3200 at gmail.com> wrote:

>
>
> On 01/15/2015 03:47 PM, Ron Adam wrote:
>
>> How about this?
>>
>>
>> def is_close(x, y, delta=.001):
>>      """ Check is x and y are close to each other. """
>>      if x == y:
>>          return True           # Can't get smaller than this.
>>      if x == 0 or y == 0:
>>          return False          # Nothing is close to zero.
>>      if abs(x) < abs(y):       # Make x the larger one.
>>          x, y = y, x
>>      if x * y < 0:             # Signs differ.
>>          x = x - 2.0 * y         # Move x and y same distance.
>>          y = -y
>>      return (x - y)/float(x) <= delta
>>
>
>
> Remove the check of one being zero, it isn't needed.
>
> def is_close(x, y, delta=.001):
>      """ Check is x and y are close to each other. """
>      if x == y:
>          return True           # Can't get smaller than this.
>      if abs(x) < abs(y):       # Make x the larger one.
>          x, y = y, x
>      if x * y < 0:             # Signs differ.
>          x = x - 2.0 * y       # Move x and y same distance.
>          y = -y
>      return (x - y)/float(x) <= delta
>
>
> If one of them is zero, then you get a ratio of one. So a delta of 1 would
> mean everything is close.
>
> -Ron
>
>
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