def first(self):
"""
Pull out the first from each group. Note: this is different than
Spark's first.
"""
# If its possible to use Spark SQL grouping do it
if self._can_use_new_school():
self._prep_new_school()
import pyspark.sql.functions as func
return self._use_aggregation(func.first)
myargs = self._myargs
mykwargs = self._mykwargs
self._prep_old_school()
def create_combiner(x):
return x.groupby(*myargs, **mykwargs).first()
def merge_value(x, y):
return create_combiner(x)
def merge_combiner(x, y):
return x
rddOfFirst = self._sortIfNeeded(
self._distributedRDD.combineByKey(create_combiner, merge_value, merge_combiner)
).values()
return Dataframe.fromDataFrameRDD(rddOfFirst, self.sql_ctx)
def median(self):
"""Compute median of groups, excluding missing values.
For multiple groupings, the result index will be a MultiIndex.
"""
self._prep_old_school()
return Dataframe.fromDataFrameRDD(self._regroup_mergedRDD().values().map(lambda x: x.median()), self.sql_ctx)
def nth(self, n, *args, **kwargs):
"""Take the nth element of each grouby."""
# TODO: Stop collecting the entire frame for each key.
self._prep_old_school()
myargs = self._myargs
mykwargs = self._mykwargs
nthRDD = self._regroup_mergedRDD().mapValues(lambda r: r.nth(n, *args, **kwargs)).values()
return Dataframe.fromDataFrameRDD(nthRDD, self.sql_ctx)
def var(self, ddof=1):
"""Compute standard deviation of groups, excluding missing values.
For multiple groupings, the result index will be a MultiIndex.
"""
self._prep_old_school()
return Dataframe.fromDataFrameRDD(
self._regroup_mergedRDD().values().map(lambda x: x.var(ddof=ddof)), self.sql_ctx
)
def mean(self):
"""Compute mean of groups, excluding missing values.
For multiple groupings, the result index will be a MultiIndex.
"""
if self._can_use_new_school():
self._prep_new_school()
import pyspark.sql.functions as func
return self._use_aggregation(func.mean)
self._prep_old_school()
return Dataframe.fromDataFrameRDD(self._regroup_mergedRDD().values().map(lambda x: x.mean()), self.sql_ctx)
def aggregate(self, f):
"""Apply the aggregation function.
Note: This implementation does note take advantage of partial
aggregation unless we have one of the special cases.
Currently the only special case is Series.kurtosis - and even
that doesn't properly do partial aggregations, but we can improve
it to do this eventually!
"""
if self._can_use_new_school() and f == pd.Series.kurtosis:
self._prep_new_school()
import custom_functions as CF
return self._use_aggregation(CF.kurtosis)
else:
self._prep_old_school()
return Dataframe.fromDataFrameRDD(
self._regroup_mergedRDD().values().map(lambda g: g.aggregate(f)), self.sql_ctx
)
def apply(self, func, *args, **kwargs):
"""Apply the provided function and combine the results together in the
same way as apply from groupby in pandas.
This returns a Dataframe.
"""
self._prep_old_school()
def key_by_index(data):
"""Key each row by its index.
"""
# TODO: Is there a better way to do this?
for key, row in data.iterrows():
yield (key, pd.DataFrame.from_dict(dict([(key, row)]), orient="index"))
myargs = self._myargs
mykwargs = self._mykwargs
regroupedRDD = self._distributedRDD.mapValues(lambda data: data.groupby(*myargs, **mykwargs))
appliedRDD = regroupedRDD.map(lambda key_data: key_data[1].apply(func, *args, **kwargs))
reKeyedRDD = appliedRDD.flatMap(key_by_index)
dataframe = self._sortIfNeeded(reKeyedRDD).values()
return Dataframe.fromDataFrameRDD(dataframe, self.sql_ctx)
def last(self):
"""Pull out the last from each group."""
myargs = self._myargs
mykwargs = self._mykwargs
# If its possible to use Spark SQL grouping do it
if self._can_use_new_school():
self._prep_new_school()
import pyspark.sql.functions as func
return self._use_aggregation(func.last)
def create_combiner(x):
return x.groupby(*myargs, **mykwargs).last()
def merge_value(x, y):
return create_combiner(y)
def merge_combiner(x, y):
return y
rddOfLast = self._sortIfNeeded(
self._distributedRDD.combineByKey(create_combiner, merge_value, merge_combiner)
).values()
return Dataframe.fromDataFrameRDD(rddOfLast, self.sql_ctx)
def max(self):
"""Compute the max for each group."""
if self._can_use_new_school():
self._prep_new_school()
import pyspark.sql.functions as func
return self._use_aggregation(func.max)
self._prep_old_school()
myargs = self._myargs
mykwargs = self._mykwargs
def create_combiner(x):
return x.groupby(*myargs, **mykwargs).max()
def merge_value(x, y):
return x.append(create_combiner(y)).max()
def merge_combiner(x, y):
return x.append(y).max(level=0)
rddOfMax = self._sortIfNeeded(
self._distributedRDD.combineByKey(create_combiner, merge_value, merge_combiner)
).values()
return Dataframe.fromDataFrameRDD(rddOfMax, self.sql_ctx)
def sum(self):
"""Compute the sum for each group."""
if self._can_use_new_school():
self._prep_new_school()
import pyspark.sql.functions as func
return self._use_aggregation(func.sum)
self._prep_old_school()
myargs = self._myargs
mykwargs = self._mykwargs
def create_combiner(x):
return x.groupby(*myargs, **mykwargs).sum()
def merge_value(x, y):
return pd.concat([x, create_combiner(y)])
def merge_combiner(x, y):
return x + y
rddOfSum = self._sortIfNeeded(
self._distributedRDD.combineByKey(create_combiner, merge_value, merge_combiner)
).values()
return Dataframe.fromDataFrameRDD(rddOfSum, self.sql_ctx)
