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/*
* Copyright (c) 2010-2021 Haifeng Li. All rights reserved.
*
* Smile is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Smile is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Smile. If not, see .
*/
package smile.plot.vega;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.ObjectNode;
/**
* The window transform performs calculations over sorted groups of data
* objects. These calculations including ranking, lead/lag analysis, and
* aggregates such as running sums and averages. Calculated values are
* written back to the input data stream. If you only want to set the same
* aggregated value in a new field, you can use the simpler join aggregate
* transform.
*
* @author Haifeng Li
*/
public class WindowTransform {
/** VegaLite's Window definition object. */
final ObjectNode spec;
/**
* Hides the constructor so that users cannot create the instances directly.
*/
WindowTransform(ObjectNode spec) {
this.spec = spec;
}
@Override
public String toString() {
return spec.toString();
}
/**
* Returns the specification in pretty print.
* @return the specification in pretty print.
*/
public String toPrettyString() {
return spec.toPrettyString();
}
/**
* Sets the frame specification indicating how the sliding window should
* proceed. It is either a number indicating the offset from the current
* data object, or null to indicate unbounded rows preceding or following
* the current data object. The default value is [null, 0], indicating that
* the sliding window includes the current object and all preceding objects.
* The value [-5, 5] indicates that the window should include five objects
* preceding and five objects following the current object. Finally,
* [null, null] indicates that the window frame should always include all
* data objects. If you this frame and want to assign the same value to add
* objects, you can use the simpler join aggregate transform. The only
* operators affected are the aggregation operations and the first_value,
* last_value, and nth_value window operations. The other window operations
* are not affected by this.
*
* @param first the offset of the first object in the sliding window.
* @param last the offset of the first object in the sliding window.
* @return this object.
*/
public WindowTransform frame(Integer first, Integer last) {
spec.putArray("frame")
.add(first == null ? null : first.intValue())
.add(last == null ? null : last.intValue());
return this;
}
/**
* Sets if the sliding window frame should ignore peer values (data that
* are considered identical by the sort criteria). The default is false,
* causing the window frame to expand to include all peer values. If set
* to true, the window frame will be defined by offset values only. This
* setting only affects those operations that depend on the window frame,
* namely aggregation operations and the first_value, last_value, and
* nth_value window operations.
*
* @param flag If true, ignore peer values.
* @return this object.
*/
public WindowTransform ignorePeers(boolean flag) {
spec.put("ignorePeers", flag);
return this;
}
/**
* Sets the data fields for partitioning the data objects into separate
* windows. If unspecified, all data points will be in a single window.
*
* @param fields the partitioning fields.
* @return this object.
*/
public WindowTransform groupby(String... fields) {
ArrayNode node = spec.putArray("groupby");
for (var field : fields) {
node.add(field);
}
return this;
}
/**
* Sets the fields for sorting data objects within a window. If two data
* objects are considered equal by the comparator, they are considered
* "peer" values of equal rank. If sort is not specified, the order is
* undefined: data objects are processed in the order they are observed
* and none are considered peers (the ignorePeers parameter is ignored
* and treated as if set to true).
*
* @param fields the partitioning fields.
* @return this object.
*/
public WindowTransform sort(String... fields) {
ArrayNode node = spec.putArray("sort");
for (var field : fields) {
node.addObject().put("field", field);
}
return this;
}
/**
* Sets the fields for sorting data objects within a window. If two data
* objects are considered equal by the comparator, they are considered
* "peer" values of equal rank. If sort is not specified, the order is
* undefined: data objects are processed in the order they are observed
* and none are considered peers (the ignorePeers parameter is ignored
* and treated as if set to true).
*
* @param fields the partitioning fields.
* @return this object.
*/
public WindowTransform sort(SortField... fields) {
ArrayNode node = spec.putArray("sort");
for (var field : fields) {
node.addObject()
.put("field", field.field())
.put("order", field.order());
}
return this;
}
}
