[Numpy-discussion] Setting small numbers to zero.

Robert Kern robert.kern@gmail....
Wed Mar 17 14:11:22 CDT 2010


On Wed, Mar 17, 2010 at 14:07,  <josef.pktd@gmail.com> wrote:
> On Wed, Mar 17, 2010 at 3:01 PM, Robert Kern <robert.kern@gmail.com> wrote:
>> On Wed, Mar 17, 2010 at 14:04, Christopher Barker <Chris.Barker@noaa.gov> wrote:
>>> Friedrich Romstedt wrote:
>>>> Code:
>>>>
>>>> import numpy
>>>> import time
>>>>
>>>> a = numpy.random.random((2000, 2000))
>>>>
>>>> start = time.time()
>>>> a[abs(a) < 10] = 0
>>>> stop = time.time()
>>>
>>> I highly recommend ipython and its "timeit" function --much better for this.
>>>
>>> And numpy.clip() may be helpful here,
>>
>> No, it's not.
>
> why not?
>
> np.clip([-1,-5,1,1e90,np.inf, np.nan], 0, np.inf)
> array([  0.00000000e+00,   0.00000000e+00,   1.00000000e+00,
>         1.00000000e+90,              Inf,              NaN])

Why do you think that's equivalent? That just clips negative numbers
to 0. The question is how to set numbers of small absolute magnitude
to 0.

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless
enigma that is made terrible by our own mad attempt to interpret it as
though it had an underlying truth."
  -- Umberto Eco


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