tech.tablesaw.table.RollingColumn Maven / Gradle / Ivy
package tech.tablesaw.table;
import tech.tablesaw.aggregate.AggregateFunction;
import tech.tablesaw.api.DoubleColumn;
import tech.tablesaw.columns.Column;
import tech.tablesaw.selection.BitmapBackedSelection;
import tech.tablesaw.selection.Selection;
import tech.tablesaw.util.StringUtils;
/**
* Does a calculation on a rolling basis (e.g. mean for last 20 days)
*/
public class RollingColumn {
protected final Column column;
protected final int window;
public RollingColumn(Column column, int window) {
this.column = column;
this.window = window;
}
protected String generateNewColumnName(AggregateFunction function) {
boolean useSpaces = column.name().matches("\\s+");
String separator = useSpaces ? " " : "";
return new StringBuilder(column.name())
.append(separator).append(useSpaces ? function.functionName() : StringUtils.capitalize(function.functionName()))
.append(separator).append(window)
.toString();
}
@SuppressWarnings({"unchecked"})
public ,OUT> Column calc(AggregateFunction function) {
// TODO: the subset operation copies the array. creating a view would likely be more efficient
Column result = function.returnType().create(generateNewColumnName(function));
for (int i = 0; i < window - 1; i++) {
result.appendMissing();
}
for (int origColIndex = 0; origColIndex < column.size() - window + 1; origColIndex++) {
Selection selection = new BitmapBackedSelection();
selection.addRange(origColIndex, origColIndex + window);
INCOL subsetCol = (INCOL) column.subset(selection.toArray());
OUT answer = function.summarize(subsetCol);
if (answer instanceof Number) {
Number number = (Number) answer;
((DoubleColumn) result).append(number.doubleValue());
} else {
result.appendObj(answer);
}
}
return result;
}
}