Where can I find mad (mean absolute deviation) in scipy?
[EDIT] Since this keeps on getting downvoted: I know that median absolute deviation is a more commonly-used statistic, but the questioner asked for mean absolute deviation, and here's how to do it:
from numpy import mean, absolutedef mad(data, axis=None): return mean(absolute(data - mean(data, axis)), axis)
For what its worth, I use this for MAD:
def mad(arr): """ Median Absolute Deviation: a "Robust" version of standard deviation. Indices variabililty of the sample. https://en.wikipedia.org/wiki/Median_absolute_deviation """ arr = np.ma.array(arr).compressed() # should be faster to not use masked arrays. med = np.median(arr) return np.median(np.abs(arr - med))
The current version of statsmodels has mad
in statsmodels.robust
:
>>> import numpy as np>>> from statsmodels import robust>>> a = np.matrix( [... [ 80, 76, 77, 78, 79, 81, 76, 77, 79, 84, 75, 79, 76, 78 ],... [ 66, 69, 76, 72, 79, 77, 74, 77, 71, 79, 74, 66, 67, 73 ]... ], dtype=float )>>> robust.mad(a, axis=1)array([ 2.22390333, 5.18910776])
Note that by default this computes the robust estimate of the standard deviation assuming a normal distribution by scaling the result a scaling factor; from help
:
Signature: robust.mad(a, c=0.67448975019608171, axis=0, center=<function median at 0x10ba6e5f0>)
The version in R
makes a similar normalization. If you don't want this, obviously just set c=1
.
(An earlier comment mentioned this being in statsmodels.robust.scale
. The implementation is in statsmodels/robust/scale.py
(see github) but the robust
package does not export scale
, rather it exports the public functions in scale.py
explicitly.)