esda.Moran_Local_BV¶

class esda.Moran_Local_BV(x, y, w, transformation='r', permutations=999, geoda_quads=False, n_jobs=1, keep_simulations=True, seed=None, island_weight=0)[source]¶

Bivariate Local Moran Statistics.

Parameters:

xarray: x-axis variable
yarray: (n,1), wy will be on y axis
wW | Graph: spatial weights instance as W or Graph aligned with y
transformation{‘R’, ‘B’, ‘D’, ‘U’, ‘V’}: weights transformation, default is row-standardized “r”. Other options include “B”: binary, “D”: doubly-standardized, “U”: untransformed (general weights), “V”: variance-stabilizing.
permutationsint: number of random permutations for calculation of pseudo p_values
geoda_quadsbool: (default=False) If True use GeoDa scheme: HH=1, LL=2, LH=3, HL=4 If False use PySAL Scheme: HH=1, LH=2, LL=3, HL=4
njobsint: number of workers to use to compute the local statistic.
keep_simulationsBoolean: (default=True) If True, the entire matrix of replications under the null is stored in memory and accessible; otherwise, replications are not saved
seedNone/int: Seed to ensure reproducibility of conditional randomizations. Must be set here, and not outside of the function, since numba does not correctly interpret external seeds nor numpy.random.RandomState instances.
island_weight:: value to use as a weight for the “fake” neighbor for every island. If numpy.nan, will propagate to the final local statistic depending on the stat_func. If 0, then the lag is always zero for islands.

Examples

>>> import libpysal
>>> import numpy as np
>>> np.random.seed(10)
>>> w = libpysal.io.open(libpysal.examples.get_path("sids2.gal")).read()
>>> f = libpysal.io.open(libpysal.examples.get_path("sids2.dbf"))
>>> x = np.array(f.by_col['SIDR79'])
>>> y = np.array(f.by_col['SIDR74'])
>>> from esda.moran import Moran_Local_BV
>>> lm =Moran_Local_BV(x, y, w, transformation = "r",                                permutations = 99)
>>> lm.q[:10]
array([3, 4, 3, 4, 2, 1, 4, 4, 2, 4])
>>> lm = Moran_Local_BV(x, y, w, transformation = "r",                                permutations = 99, geoda_quads=True)
>>> lm.q[:10]
array([2, 4, 2, 4, 3, 1, 4, 4, 3, 4])

Note random components result is slightly different values across architectures so the results have been removed from doctests and will be moved into unittests that are conditional on architectures.

Attributes:

zxarray: original x variable standardized by mean and std
zyarray: original y variable standardized by mean and std
wW | Graph: original w object
permutationsint: number of random permutations for calculation of pseudo p_values
Isfloat: value of Moran’s I
qarray: (if permutations>0) values indicate quandrant location 1 HH, 2 LH, 3 LL, 4 HL
simarray: (if permutations>0) vector of I values for permuted samples
p_simarray: (if permutations>0) p-value based on permutations (one-sided) null: spatial randomness alternative: the observed Ii is further away or extreme from the median of simulated values. It is either extremelyi high or extremely low in the distribution of simulated Is.
EI_simarray: (if permutations>0) average values of local Is from permutations
VI_simarray: (if permutations>0) variance of Is from permutations
seI_sim: array: (if permutations>0) standard deviations of Is under permutations.
z_simarrray: (if permutations>0) standardized Is based on permutations
p_z_sim: array: (if permutations>0) p-values based on standard normal approximation from permutations (one-sided) for two-sided tests, these values should be multiplied by 2

__init__(x, y, w, transformation='r', permutations=999, geoda_quads=False, n_jobs=1, keep_simulations=True, seed=None, island_weight=0)[source]¶

Methods

`__init__`(x, y, w[, transformation, ...])
`by_col`(df, x[, y, w, inplace, pvalue, outvals])	Function to compute a Moran_Local_BV statistic on a dataframe

classmethod by_col(df, x, y=None, w=None, inplace=False, pvalue='sim', outvals=None, **stat_kws)[source]¶

Function to compute a Moran_Local_BV statistic on a dataframe

Parameters:

dfpandas.DataFrame: a pandas dataframe with a geometry column
Xlist of strings: column name or list of column names to use as X values to compute the bivariate statistic. If no Y is provided, pairwise comparisons among these variates are used instead.
Ylist of strings: column name or list of column names to use as Y values to compute the bivariate statistic. if no Y is provided, pariwise comparisons among the X variates are used instead.
wW | Graph: spatial weights instance as W or Graph aligned with the dataframe. If not provided, this is searched for in the dataframe’s metadata
inplacebool: a boolean denoting whether to operate on the dataframe inplace or to return a series contaning the results of the computation. If operating inplace, the derived columns will be named ‘column_moran_local_bv’
pvaluestr: a string denoting which pvalue should be returned. Refer to the the Moran_Local_BV statistic’s documentation for available p-values
outvalslist of strings: list of arbitrary attributes to return as columns from the Moran_Local_BV statistic
**stat_kwsdict: options to pass to the underlying statistic. For this, see the documentation for the Moran_Local_BV statistic.

Returns:

If inplace, None, and operation is conducted on dataframe
in memory. Otherwise, returns a copy of the dataframe with
the relevant columns attached.