---
title: "VelocityTracker1D"
description: "A velocity tracker calculating velocity in 1 dimension.

Add displacement data points using [addDataPoint], and obtain velocity using [calculateVelocity].

Note: for calculating touch-related or other 2 dimensional/planar velocities, please use
[VelocityTracker], which handles velocity tracking across both X and Y dimensions at once."
type: "class"
---

<div class='type'>Class</div>


<a id='references'></a>

<div class='sourceset sourceset-common'>Common</div>


```kotlin
class VelocityTracker1D
internal constructor(
    val isDataDifferential: Boolean = false,
    private val strategy: Strategy = Strategy.Lsq2,
)
```


A velocity tracker calculating velocity in 1 dimension.

Add displacement data points using `addDataPoint`, and obtain velocity using `calculateVelocity`.

Note: for calculating touch-related or other 2 dimensional/planar velocities, please use
`VelocityTracker`, which handles velocity tracking across both X and Y dimensions at once.


## Secondary Constructors

```kotlin
constructor(isDataDifferential: Boolean) : this(isDataDifferential, Strategy.Impulse)
```


Constructor to create a new velocity tracker. It allows to specify whether or not the tracker
should consider the data ponits provided via `addDataPoint` as differential or
non-differential.

Differential data ponits represent change in displacement. For instance, differential data
points of `2, -1, 5` represent: the object moved by "2" units, then by "-1" units, then by
"5" units. An example use case for differential data points is when tracking velocity for an
object whose displacements (or change in positions) over time are known.

Non-differential data ponits represent position of the object whose velocity is tracked. For
instance, non-differential data points of `2, -1, 5` represent: the object was at position
"2", then at position "-1", then at position "5". An example use case for non-differential
data points is when tracking velocity for an object whose positions on a geometrical axis
over different instances of time are known.

#### Parameters

| | |
| --- | --- |
| isDataDifferential | `true` if the data ponits provided to the constructed tracker are differential. `false` otherwise. |



## Functions

```kotlin
fun addDataPoint(timeMillis: Long, dataPoint: Float)
```


Adds a data point for velocity calculation at a given time, `timeMillis`. The data ponit
represents an amount of a change in position (for differential data points), or an absolute
position (for non-differential data points). Whether or not the tracker handles differential
data points is decided by `isDataDifferential`, which is set once and finally during the
construction of the tracker.

Use the same units for the data points provided. For example, having some data points in `cm`
and some in `m` will result in incorrect velocity calculations, as this method (and the
tracker) has no knowledge of the units used.


```kotlin
fun calculateVelocity(): Float
```


Computes the estimated velocity at the time of the last provided data point.

The units of velocity will be `units/second`, where `units` is the units of the data points
provided via `addDataPoint`.

This can be expensive. Only call this when you need the velocity.


```kotlin
fun calculateVelocity(maximumVelocity: Float): Float
```


Computes the estimated velocity at the time of the last provided data point.

The method allows specifying the maximum absolute value for the calculated velocity. If the
absolute value of the calculated velocity exceeds the specified maximum, the return value
will be clamped down to the maximum. For example, if the absolute maximum velocity is
specified as "20", a calculated velocity of "25" will be returned as "20", and a velocity of
"-30" will be returned as "-20".

#### Parameters

| | |
| --- | --- |
| maximumVelocity | the absolute value of the maximum velocity to be returned in units/second, where `units` is the units of the positions provided to this VelocityTracker. |



```kotlin
fun resetTracking()
```


Clears data points added by `addDataPoint`.