tech.tablesaw.analytic.WindowSlider Maven / Gradle / Ivy
package tech.tablesaw.analytic;
import java.util.function.Function;
import tech.tablesaw.analytic.WindowFrame.WindowGrowthType;
import tech.tablesaw.columns.Column;
import tech.tablesaw.table.TableSlice;
/**
* Execute the aggregate function once for every row in the slice.
*
* Any window with a Fixed end (UNBOUNDED FOLLOWING) is converted ("mirrored") into the
* equivalent UNBOUNDED PRECEDING widow so that it is an append window and a faster algorithm can be
* used.
*/
class WindowSlider {
private final boolean mirrored;
private final WindowGrowthType windowGrowthType;
private final int initialLeftBound;
private final int initialRightBound;
@SuppressWarnings({"unchecked", "rawtypes"})
private final AggregateFunction function;
private final TableSlice slice;
private final Column sourceColumn;
@SuppressWarnings({"unchecked", "rawtypes"})
private final Column destinationColumn;
WindowSlider(
WindowFrame windowFrame,
AggregateFunctions func,
TableSlice slice,
Column sourceColumn,
Column destinationColumn) {
this.slice = slice;
this.destinationColumn = destinationColumn;
this.sourceColumn = sourceColumn;
this.function = func.getImplementation(windowFrame.windowGrowthType());
// Convert UNBOUNDED FOLLOWING to an equivalent UNBOUNDED PRECEDING window.
if (windowFrame.windowGrowthType() == WindowGrowthType.FIXED_RIGHT) {
this.windowGrowthType = WindowGrowthType.FIXED_LEFT;
this.mirrored = true;
this.initialLeftBound = windowFrame.getInitialRightBound() * -1;
this.initialRightBound = windowFrame.getInitialLeftBound() * -1;
} else {
this.mirrored = false;
this.initialLeftBound = windowFrame.getInitialLeftBound();
this.initialRightBound = windowFrame.getInitialRightBound();
this.windowGrowthType = windowFrame.windowGrowthType();
}
}
/** Slide the window over the slice calculating an aggregate value for every row in the slice. */
@SuppressWarnings({"unchecked", "rawtypes"})
void execute() {
initWindow();
// Initial window bounds can be outside the current slice. This allows for windows like 20
// PRECEDING 10 PRECEDING
// to slide into the slice. Rows outside the slide will be ignored.
int leftBound = getInitialLeftBound() - 1;
int rightBound = getInitialRightBound();
for (int i = 0; i < slice.rowCount(); i++) {
this.set(i, function.getValue());
// Slide the left side of the window if applicable for the window definition.
int newLeftBound = slideLeftStrategy().apply(leftBound);
if (newLeftBound > leftBound && isRowNumberInSlice(newLeftBound)) {
// If the left side of the window changed remove the left most value from the aggregate
// function.
function.removeLeftMost();
}
leftBound = newLeftBound;
// Slide the right side of the window if applicable for the window definition.
int newRightBound = slideRightStrategy().apply(rightBound);
if (newRightBound > rightBound && isRowNumberInSlice(newRightBound)) {
// If the right side of the window changed add the next value to the aggregate function.
if (isMissing(newRightBound)) {
function.addRightMostMissing();
} else {
function.addRightMost(get(newRightBound));
}
}
rightBound = newRightBound;
}
}
/**
* Returns the mirrored index about the center of the window. Used to convert UNBOUNDED FOLLOWING
* windows to UNBOUNDED PRECEDING windows.
*/
int mirror(int rowNumber) {
if (this.mirrored) {
return slice.rowCount() - rowNumber - 1;
}
return rowNumber;
}
/**
* Adds initial values to the aggregate function for the first window. E.G. ROWS BETWEEN CURRENT
* ROW AND 3 FOLLOWING would add the first four rows in the slice to the function.
*/
@SuppressWarnings({"unchecked", "rawtypes"})
private void initWindow() {
int leftBound = Math.max(getInitialLeftBound(), 0);
int rightBound = Math.min(getInitialRightBound(), slice.rowCount() - 1);
for (int i = leftBound; i <= rightBound; i++) {
if (isMissing(i)) {
function.addRightMostMissing();
} else {
function.addRightMost(get(i));
}
}
}
/** Set the value in the destination column that corresponds to the row in the view. */
@SuppressWarnings({"unchecked", "rawtypes"})
private void set(int rowNumberInSlice, Object value) {
destinationColumn.set(slice.mappedRowNumber(mirror(rowNumberInSlice)), value);
}
/** Get a value from the source column that corresponds to the row in the view. */
private Object get(int rowNumberInSlice) {
return sourceColumn.get(slice.mappedRowNumber(mirror(rowNumberInSlice)));
}
/**
* Determine if the value in the source column that corresponds to the row in the view is missing.
*/
private boolean isMissing(int rowNumberInSlice) {
return sourceColumn.isMissing(slice.mappedRowNumber(mirror(rowNumberInSlice)));
}
/** Returns true of the rowNumber exists in the slice. */
private boolean isRowNumberInSlice(int rowNumber) {
return rowNumber >= 0 && rowNumber < slice.rowCount();
}
private Function slideLeftStrategy() {
switch (this.windowGrowthType) {
case FIXED:
case FIXED_LEFT:
return i -> i;
case SLIDING:
return i -> i + 1;
}
throw new IllegalArgumentException("Unexpected growthType: " + this.windowGrowthType);
}
private Function slideRightStrategy() {
switch (this.windowGrowthType) {
case FIXED:
return i -> i;
case FIXED_LEFT:
case SLIDING:
return i -> i + 1;
}
throw new IllegalArgumentException("Unexpected growthType: " + this.windowGrowthType);
}
private int getInitialLeftBound() {
// is zero for FIXED and FIXED_LEFT windows.
return this.initialLeftBound;
}
private int getInitialRightBound() {
switch (this.windowGrowthType) {
case FIXED:
return slice.rowCount() - 1;
case FIXED_LEFT:
case SLIDING:
return this.initialRightBound;
}
throw new IllegalArgumentException("Unexpected growthType: " + this.windowGrowthType);
}
}