resolve discrepancy of estimating Moran's I corrected for rates between GeoDa and pysal

[weikang9009]

This PR is to reopen PR #989 which was unmerged but closed because of some complication I made. It is to resolve the discrepancy in estimating EBI (Moran's I corrected for rates) between GeoDa and pysal as pointed out in issue #987. Now users could choose to conform with Geoda by setting parameter geoda_rate=True :

pysal.esda.moran.Moran_Local(e, b, w, adjusted=True, transformation = "r", geoda_rate=True)
pysal.esda.moran.Moran_Local_Rate(e, b, w, adjusted=True, transformation = "r", geoda_rate=True)

or to use the original implementation of correcting rates in pysal which conform with the Assunção's paper by setting parameter geoda_rate=False:

pysal.esda.moran.Moran_Local(e, b, w, adjusted=True, transformation = "r", geoda_rate=False)
pysal.esda.moran.Moran_Local_Rate(e, b, w, adjusted=True, transformation = "r", geoda_rate=False)

[coveralls]

Coverage increased (+0.02%) to 83.668% when pulling efba47a on weikang9009:moran_rates into 8d1e596 on pysal:master.

[sjsrey]

Looks good. One question on "geoda_rate": we only discuss T/F for this when adjusted=True. What is the behavior when adjusted=False?

[sjsrey]

Adding a note here that when this gets merged, we need to port to https://github.com/pysal/esda

[weikang9009]

@sjsrey If adjusted=True (or geoda_rate=False in function assuncao_rate and related Moran and local Moran classes) , conform with Assuncao and Reis (1999), that is, assign v_i = a+b/x_i and check individual v_i: if v_i<0, assign v_i = b/x_i.

[sjsrey]

@weikang9009 if adjusted=False, is geoda_rate ignored?

[weikang9009]

@sjsrey yes. If adjusted=False, geoda_rate is ignored. Moran statistics won't be adjusted for rates.

[sjsrey]

@weikang9009 maybe we should add to the docs that:

If adjusted=False, geoda_rate is ignored

[coveralls]

Coverage increased (+0.005%) to 83.668% when pulling add8409 on weikang9009:moran_rates into 94cdbf7 on pysal:master.

[weikang9009]

@sjsrey Thank you for the suggestion. Have updated the docs (for Moran_Rate and Moran_Local_Rate).