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# medpy.metric.histogram.relative_deviation¶

medpy.metric.histogram.relative_deviation(h1, h2)[source]

Calculate the deviation between two histograms.

The relative deviation between two histograms $$H$$ and $$H'$$ of size $$m$$ is defined as:

$d_{rd}(H, H') = \frac{ \sqrt{\sum_{m=1}^M(H_m - H'_m)^2} }{ \frac{1}{2} \left( \sqrt{\sum_{m=1}^M H_m^2} + \sqrt{\sum_{m=1}^M {H'}_m^2} \right) }$

Attributes:

• semimetric (triangle equation satisfied?)

Attributes for normalized histograms:

• $$d(H, H')\in[0, \sqrt{2}]$$
• $$d(H, H) = 0$$
• $$d(H, H') = d(H', H)$$

Attributes for not-normalized histograms:

• $$d(H, H')\in[0, 2]$$
• $$d(H, H) = 0$$
• $$d(H, H') = d(H', H)$$

Attributes for not-equal histograms:

• not applicable
Parameters: h1 : sequence The first histogram. h2 : sequence The second histogram, same bins as h1. relative_deviation : float Relative deviation between the two histograms.