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luoyetx / face-alignment-at-3000fps

C++ implementation of Face Alignment at 3000 FPS via Regressing Local Binary Features
BSD 3-Clause "New" or "Revised" License
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variance question #15

Open jeremywrightkim opened 7 years ago

jeremywrightkim commented 7 years ago

I understood this code. 'double m1 = cv::mean(vec)[0];' 'double m2 = cv::mean(vec.mul(vec_))[0];' 'double variance = m2 - m1*m1;'

But I don't understand formula below. 'double variance_all = (calcVariance(delta_shapes.col(0)) + calcVariance(delta_shapes.col(1)))*N;'

Does 2-D variance addition each 1-dimensional variance? What means of N? N is count of training sample. But I don't understand why multiply N.

Could you please provide some reference material?