[Numpy-discussion] what is the best way to do a statistical mode operation?

josef.pktd@gmai... josef.pktd@gmai...
Sun Oct 3 07:55:38 CDT 2010


On Sun, Oct 3, 2010 at 8:41 AM, Gordon Wrigley <gordon@tolomea.com> wrote:
> I have an array of uint8's that has a shape of X*Y*Z*8, I would like to
> calculate modes along the 8 axis so that I end up with an array that has the
> shape X*Y*Z and is full of modes.
> I'm having problems finding a good way of doing this. My attempts at solving
> this using bincount or histogram produce an intermediate array that is 32x
> the size of my input data and somewhat larger than I have the memory to deal
> with.
> Can anyone suggest a good way to produce modes over sets of 8 bytes?
> Also in the instance where there are multiple modes for a particular set I'm
> happy for it to pick any one arbitrarily.

What's the range of integers? How many point do you have in np.unique(array) ?

bincount, for example, uses range(arr.max()+1) as set of points.

looping over 8 values would be fast, but the intermediate arrays would
depend on the number of unique values.
I would try to use a dictionary.

Josef


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