water.rapids.ast.prims.advmath

Class AstImpute

java.lang.Object

water.Iced<T>

water.rapids.ast.AstRoot<T>

water.rapids.ast.AstPrimitive

water.rapids.ast.prims.advmath.AstImpute

All Implemented Interfaces:

java.io.Externalizable, java.io.Serializable, java.lang.Cloneable, Freezable

public class AstImpute
extends AstPrimitive

Impute columns of a data frame in place.

This impute can impute whole Frames or a specific Vec within the Frame. Imputation will be by the default mean (for numeric columns) or mode (for categorical columns). String, date, and UUID columns are never imputed.

When a Vec is specified to be imputed, it can alternatively be imputed by grouping on some other columns in the Frame. If groupByCols is specified, but the user does not supply a column to be imputed then an IllegalArgumentException will be raised. Further, if the user specifies the column to impute within the groupByCols, exceptions will be raised.

The methods that a user may impute by are as follows: - mean: Vec.T_NUM - median: Vec.T_NUM - mode: Vec.T_CAT - bfill: Any valid Vec type - ffill: Any valid Vec type

All methods of imputation are done in place! The first three methods (mean, median, mode) are self-explanatory. The bfill and ffill methods will attempt to fill NAs using adjacent cell value (either before or forward):

Vec = [ bfill_value, NA, ffill_value] | ^^ | -> || <- impute

If the impute method is median then the combineMethod can be one of the Enum variants of QuantileModel.CombineMethod = { INTERPOLATE, AVERAGE, LOW, HIGH }. The Enum specifies how to combine quantiles on even sample sizes. This parameter is ignored in all other cases.

Finally, the groupByFrame can be used to impute a column with a pre-computed groupby result.

Other notes:

If col is -1, then the entire Frame will be imputed using mean/mode where appropriate.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
AstImpute()

Method Summary

Modifier and Type	Method and Description
Val	apply(Env env, Env.StackHelp stk, AstRoot[] asts) Primary method to invoke this function, passing all the parameters as the `asts` list.
java.lang.String[]	args() List of argument names.
int	nargs() Number of function's arguments + 1.
java.lang.String	str() String representation of this Ast object in the Rapids language.

Methods inherited from class water.rapids.ast.AstPrimitive

description, example, exec

Methods inherited from class water.rapids.ast.AstRoot

toString

Methods inherited from class water.Iced

asBytes, clone, copyOver, frozenType, read, readExternal, readJSON, reloadFromBytes, toJsonBytes, toJsonString, write, writeExternal, writeJSON

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

AstImpute

public AstImpute()

Method Detail

args

public java.lang.String[] args()

Description copied from class: AstPrimitive

List of argument names. The length of the returned array should be equal to `nargs() - 1` (unless `nargs()` returns -1, in which case this function may return {"..."} or something similar).

Specified by:

args in class AstPrimitive

str

public java.lang.String str()

Description copied from class: AstRoot

String representation of this Ast object in the Rapids language. For AstPrimitives this is the name of the function; for AstParameters this is either the name of the variable, or the value of the numeric constant that the parameter represents. For more complicated constructs such as AstExec or AstFunction this method should return those objects as a Rapids string.

Specified by:

str in class AstRoot

nargs

public int nargs()

Description copied from class: AstPrimitive

Number of function's arguments + 1. Thus, a binary operator like '+' should be declared with 3 nargs: ["+", lhs, rhs]. For variable-argument functions this method should return -1.

Specified by:

nargs in class AstPrimitive

apply

public Val apply(Env env,
                 Env.StackHelp stk,
                 AstRoot[] asts)

Description copied from class: AstPrimitive

Primary method to invoke this function, passing all the parameters as the `asts` list.

Specified by:

apply in class AstPrimitive

Parameters:

env - Current execution environment. Variables are looked up here.

stk - TODO need clarification

asts - List of AstRoot expressions that are arguments to the function. First element in this list is the function itself.

Returns:

value resulting from calling the function with the provided list of arguments.