nafeesb/numpy.md

## numpy.md

      
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              numpy.md
            
          
    Ouput Zero for divide by zero

length_err_pct = np.divide( pred_length, true_length, out=np.zeros_like(pred_length), where=true_length!=0)
Random subset of indices

sel = np.random.choice(testX.shape[0], samples, replace=False)
Save formatting

np.savetxt(phasefile,phase,fmt='%.6f')
zip mismatched array

for line in itertools.zip_longest( *plants, fillvalue=''):
    f.write('%s %s\n' % line)
Image processing

Save using PIL

yimg = Image.fromarray((out * 255).astype(np.uint8))
yimg.save('nnout.jpg')
Structs

List struct fields: S.dtype.fields
PCA

Explained variance

evr = model.explained_variance_ratio_
cumulative_evr = np.cumsum(evr)

# Number of components needed to explain 95% of variance.
np.argmax( cumulative_evr >= 0.95 ) + 1