def kNNimputeMA(arr2d, K=20, callback=None):
"""Returns a new 2D MA.array with missing values imputed from K nearest neighbours.
Find K rows (axis 0) with the most similar values where similarity measure corresponds to weighted Euclidean distance.
Imputed value = weighted average of the corresponding values of K nearest neighbours,
where weights equal to tricubic distribution of distances to all rows.
Impute missing rows by average over all rows.
Version: 30.8.2005
"""
arr2d = MA.asarray(arr2d)
assert len(arr2d.shape) == 2, "2D array expected"
# make a copy for imputation
aImp2 = MA.array(arr2d)
# leave out columns with 0 known values (columnInd: non-zero columns)
columnCond = Numeric.greater(MA.count(arr2d, axis=0), 0)
columnIndAll = Numeric.arange(arr2d.shape[1])
columnInd = Numeric.compress(columnCond, columnIndAll)
# impute the rows where 0 < #known_values < #non_zero_columns, i.e. exclude the rows with 0 and all (non-zero-column) values
countByRows = MA.count(arr2d, axis=1)
for rowIdx in Numeric.compress(Numeric.logical_and(Numeric.greater(countByRows, 0), Numeric.less(countByRows, columnInd.shape[0])), Numeric.arange(arr2d.shape[0])):
rowResized = MA.resize(arr2d[rowIdx], arr2d.shape)
diff = arr2d - rowResized
distances = MA.sqrt(MA.add.reduce((diff)**2, 1) / MA.count(diff, axis=1))
# nearest neighbours row indices (without the current row index)
indSorted = MA.argsort(distances)[1:]
distSorted = distances.take(indSorted)
# number of distances different from MA.masked
numNonMasked = distSorted.shape[0] - Numeric.add.reduce(Numeric.asarray(MA.getmaskarray(distSorted), Numeric.Int))
# number of distances to account for (K or less)
if numNonMasked > 1:
weightsSorted = MA.power(1-MA.power(distSorted/distSorted[numNonMasked-1],3),3) # tricubic distribution of all weights
else:
weightsSorted = Numeric.ones(distSorted.shape[0])
# compute average for each column separately in order to account for K non-masked values
colInd4CurrRow = Numeric.compress(Numeric.logical_and(MA.getmaskarray(arr2d[rowIdx]), columnCond), columnIndAll)
for colIdx in colInd4CurrRow:
# column values sorted by distances
columnVals = arr2d[:,colIdx].take(indSorted)
# take only those weights where columnVals does not equal MA.masked
weightsSortedCompressed = MA.compress(1-MA.getmaskarray(columnVals), weightsSorted)
# impute from K (or possibly less) values
aImp2[rowIdx,colIdx] = MA.average(columnVals.compressed()[:K], weights=weightsSortedCompressed[:K])
if callback:
callback()
# impute the unknown rows with average profile
avrgRow = MA.average(arr2d, 0)
for rowIdx in Numeric.compress(Numeric.equal(countByRows, 0), Numeric.arange(arr2d.shape[0])):
aImp2[rowIdx] = avrgRow
if callback:
callback()
return aImp2
def centerMean(nm, axis=0):
"""Returns new masked numarray with values centered by subtracting Median."""
nm = numpyExtn.swapaxesMA(MA.asarray(nm, Numeric.Float), 0, axis)
return numpyExtn.swapaxesMA(nm - MA.average(nm,0), 0, axis)
def centerMean(nm, axis=0):
"""Returns new masked numarray with values centered by subtracting Median."""
nm = numpyExtn.swapaxesMA(MA.asarray(nm, Numeric.Float), 0, axis)
return numpyExtn.swapaxesMA(nm - MA.average(nm, 0), 0, axis)
def kNNimputeMA(arr2d, K=20, callback=None):
"""Returns a new 2D MA.array with missing values imputed from K nearest neighbours.
Find K rows (axis 0) with the most similar values where similarity measure corresponds to weighted Euclidean distance.
Imputed value = weighted average of the corresponding values of K nearest neighbours,
where weights equal to tricubic distribution of distances to all rows.
Impute missing rows by average over all rows.
Version: 30.8.2005
"""
arr2d = MA.asarray(arr2d)
assert len(arr2d.shape) == 2, "2D array expected"
# make a copy for imputation
aImp2 = MA.array(arr2d)
# leave out columns with 0 known values (columnInd: non-zero columns)
columnCond = Numeric.greater(MA.count(arr2d, axis=0), 0)
columnIndAll = Numeric.arange(arr2d.shape[1])
columnInd = Numeric.compress(columnCond, columnIndAll)
# impute the rows where 0 < #known_values < #non_zero_columns, i.e. exclude the rows with 0 and all (non-zero-column) values
countByRows = MA.count(arr2d, axis=1)
for rowIdx in Numeric.compress(
Numeric.logical_and(Numeric.greater(countByRows, 0),
Numeric.less(countByRows, columnInd.shape[0])),
Numeric.arange(arr2d.shape[0])):
rowResized = MA.resize(arr2d[rowIdx], arr2d.shape)
diff = arr2d - rowResized
distances = MA.sqrt(
MA.add.reduce((diff)**2, 1) / MA.count(diff, axis=1))
# nearest neighbours row indices (without the current row index)
indSorted = MA.argsort(distances)[1:]
distSorted = distances.take(indSorted)
# number of distances different from MA.masked
numNonMasked = distSorted.shape[0] - Numeric.add.reduce(
Numeric.asarray(MA.getmaskarray(distSorted), Numeric.Int))
# number of distances to account for (K or less)
if numNonMasked > 1:
weightsSorted = MA.power(
1 - MA.power(distSorted / distSorted[numNonMasked - 1], 3),
3) # tricubic distribution of all weights
else:
weightsSorted = Numeric.ones(distSorted.shape[0])
# compute average for each column separately in order to account for K non-masked values
colInd4CurrRow = Numeric.compress(
Numeric.logical_and(MA.getmaskarray(arr2d[rowIdx]), columnCond),
columnIndAll)
for colIdx in colInd4CurrRow:
# column values sorted by distances
columnVals = arr2d[:, colIdx].take(indSorted)
# take only those weights where columnVals does not equal MA.masked
weightsSortedCompressed = MA.compress(
1 - MA.getmaskarray(columnVals), weightsSorted)
# impute from K (or possibly less) values
aImp2[rowIdx,
colIdx] = MA.average(columnVals.compressed()[:K],
weights=weightsSortedCompressed[:K])
if callback:
callback()
# impute the unknown rows with average profile
avrgRow = MA.average(arr2d, 0)
for rowIdx in Numeric.compress(Numeric.equal(countByRows, 0),
Numeric.arange(arr2d.shape[0])):
aImp2[rowIdx] = avrgRow
if callback:
callback()
return aImp2