Package org.onebusaway.utility

Class TransitInterpolationLibrary

java.lang.Object

org.onebusaway.utility.TransitInterpolationLibrary

public class TransitInterpolationLibrary
extends Object

Transit-specific methods to support searching for deviations (produced from real-time predictions) for a given stop. Interpolation behavior is consistent with the GTFS-realtime spec (https://developers.google.com/transit/gtfs-realtime/) when using the EInRangeStrategy.PREVIOUS_VALUE and EOutOfRangeStrategy.LAST_VALUE strategies - in particular, this applies to the propagation of delays downstream in a trip. The EInRangeStrategy.INTERPOLATE and EOutOfRangeStrategy.INTERPOLATE strategies have behavior consistent with the normal InterpolationLibrary, which do not conform to the GTFS-rt spec.

Constructor Summary

Constructors

Constructor	Description
TransitInterpolationLibrary()

Method Summary

Modifier and Type	Method	Description
static Double	interpolate(double[] keys, double[] values, double target, EOutOfRangeStrategy outOfRangeStrategy)
static Double	interpolate(double[] keys, double[] values, double target, EOutOfRangeStrategy outOfRangeStrategy, EInRangeStrategy inRangeStrategy)	Find the deviation that should be used for a particular stop, given sorted keys (arrival times) and values (deviations) arrays.

Methods inherited from class java.lang.Object

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

Constructor Detail

TransitInterpolationLibrary

public TransitInterpolationLibrary()

Method Detail

interpolate

public static Double interpolate(double[] keys,
                                 double[] values,
                                 double target,
                                 EOutOfRangeStrategy outOfRangeStrategy)

interpolate

public static Double interpolate(double[] keys,
                                 double[] values,
                                 double target,
                                 EOutOfRangeStrategy outOfRangeStrategy,
                                 EInRangeStrategy inRangeStrategy)

Find the deviation that should be used for a particular stop, given sorted keys (arrival times) and values (deviations) arrays. The target is the arrival time for the stop we're searching for. Delay propagation is consistent with the GTFS-realtime spec (https://developers.google.com/transit/gtfs-realtime/) when using the EInRangeStrategy.PREVIOUS_VALUE and EOutOfRangeStrategy.LAST_VALUE strategies. If EOutOfRangeStrategy.LAST_VALUE is provided and all deviations are downstream from the target stop, null will be returned to indicate that no real-time information is available for the target stop. If EInRangeStrategy.INTERPOLATE is provided, this method will interpolate using linear interpolation and produce a value for a target key within the key-range of the map. For a key outside the range of the keys of the map, the outOfRange EOutOfRangeStrategy strategy will determine the interpolation behavior. EOutOfRangeStrategy.INTERPOLATE will linearly extrapolate the value.

Parameters:

keys - sorted array of keys (the scheduled arrival time of the stop)

values - sorted arrays of values (the list of real-time deviations for the provided stops)

target - the target key used to interpolate a value (the scheduled arrival time of the stop)

outOfRangeStrategy - the strategy to use for a target key that outside the key-range of the value map (use EOutOfRangeStrategy.LAST_VALUE for GTFS-rt behavior)

inRangeStrategy - the strategy to use for a target key that inside the key-range of the value map (use EInRangeStrategy.PREVIOUS_VALUE for GTFS-rt behavior)

Returns:

an interpolated value (deviation) for the target key, or null if the target is upstream of the deviations