def normalize(self, columns):
"""
Normalize numeric columns
:param columns: list of column names
:return: FeatureTable
"""
df = self.df
types = [x[1] for x in self.df.select(*columns).dtypes]
scalar_cols = [
columns[i] for i in range(len(columns))
if types[i] == "int" or types[i] == "bigint" or types[i] == "float"
or types[i] == "double"
]
array_cols = [
columns[i] for i in range(len(columns))
if types[i] == "array<int>" or types[i] == "array<bigint>"
or types[i] == "array<float>" or types[i] == "array<double>"
]
vector_cols = [
columns[i] for i in range(len(columns)) if types[i] == "vector"
]
if scalar_cols:
assembler = VectorAssembler(inputCols=scalar_cols,
outputCol="vect")
# MinMaxScaler Transformation
scaler = MinMaxScaler(inputCol="vect", outputCol="scaled")
# Pipeline of VectorAssembler and MinMaxScaler
pipeline = Pipeline(stages=[assembler, scaler])
tolist = udf(lambda x: x.toArray().tolist(),
ArrayType(DoubleType()))
# Fitting pipeline on dataframe
df = pipeline.fit(df).transform(df) \
.withColumn("scaled_list", tolist(pyspark_col("scaled"))) \
.drop("vect").drop("scaled")
for i in range(len(scalar_cols)):
df = df.withColumn(scalar_cols[i],
pyspark_col("scaled_list")[i])
df = df.drop("scaled_list")
# cast to float
for c in scalar_cols:
df = df.withColumn(c, pyspark_col(c).cast("float"))
for c in array_cols:
df = normalize_array(df, c)
for c in vector_cols:
scaler = MinMaxScaler(inputCol=c, outputCol="scaled")
df = scaler.fit(df).transform(df).withColumnRenamed("scaled", c)
return FeatureTable(df)
def add_feature(self, item_cols, feature_tbl, default_value):
"""
Get the category or other field from another map like FeatureTable
:param item_cols: list[string]
:param feature_tbl: FeatureTable with two columns [category, item]
:param defalut_cat_index: default value for category if key does not exist
:return: FeatureTable
"""
item2cat_map = dict(feature_tbl.df.distinct().rdd.map(lambda row: (row[0], row[1]))
.collect())
def gen_cat(items):
getcat = lambda item: item2cat_map.get(item, default_value)
if isinstance(items, int):
cats = getcat(items)
elif isinstance(items, list) and isinstance(items[0], int):
cats = [getcat(item) for item in items]
elif isinstance(items, list) and isinstance(items[0], list) and isinstance(items[0][0],
int):
cats = []
for line in items:
line_cats = [getcat(item) for item in line]
cats.append(line_cats)
else:
raise ValueError('only int, list[int], and list[list[int]] are supported.')
return cats
df = self.df
for c in item_cols:
col_type = df.schema[c].dataType
cat_udf = udf(gen_cat, col_type)
df = df.withColumn(c.replace("item", "category"), cat_udf(pyspark_col(c)))
return FeatureTable(df)
def cast(self, columns, type):
"""
Cast columns to the specified type.
:param columns: a string or a list of strings that specifies column names.
If it is None, then cast all of the columns.
:param type: a string ("string", "boolean", "int", "long", "short", "float", "double")
that specifies the type.
:return: A new Table that casts all of the specified columns to the specified type.
"""
if columns is None:
columns = self.df.columns
elif not isinstance(columns, list):
columns = [columns]
check_col_exists(self.df, columns)
valid_types = ["str", "string", "bool", "boolean", "int",
"integer", "long", "short", "float", "double"]
if not (isinstance(type, str) and (type in valid_types)) \
and not isinstance(type, DataType):
raise ValueError(
"type should be string, boolean, int, long, short, float, double.")
transform_dict = {"str": "string", "bool": "boolean", "integer": "int"}
type = transform_dict[type] if type in transform_dict else type
df_cast = self._clone(self.df)
for i in columns:
df_cast.df = df_cast.df.withColumn(i, pyspark_col(i).cast(type))
return df_cast
def transform_python_udf(self, in_col, out_col, udf_func):
"""
Transform a FeatureTable using a python udf
:param in_col: string, name of column needed to be transformed.
:param out_col: string, output column.
:param udf_func: user defined python function
:return: FeatureTable
"""
df = self.df.withColumn(out_col, udf_func(pyspark_col(in_col)))
return FeatureTable(df)
def add(self, columns, value=1):
"""
Increase all of values of the target numeric column(s) by a constant value.
:param columns: str or list of str, the target columns to be increased.
:param value: numeric (int/float/double/short/long), the constant value to be added.
:return: A new Table with updated numeric values on specified columns.
"""
if columns is None:
raise ValueError("Columns should be str or list of str, but got None")
if not isinstance(columns, list):
columns = [columns]
check_col_exists(self.df, columns)
new_df = self.df
for column in columns:
if new_df.schema[column].dataType not in [IntegerType(), ShortType(),
LongType(), FloatType(),
DecimalType(), DoubleType()]:
raise ValueError("Column type should be numeric, but have type {} \
for column {}".format(new_df.schema[column].dataType, column))
new_df = new_df.withColumn(column, pyspark_col(column) + lit(value))
return self._clone(new_df)
def col(self, name):
return pyspark_col(name)
