Arduino Moving Average Library

https://github.com/JChristensen/movingAvg
README file
Jack Christensen
Mar 2012

License

Arduino movingAvg Library Copyright (C) 2018 Jack Christensen GNU GPL v3.0

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License v3.0 as published by the Free Software Foundation.

This program 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 this program. If not, see https://www.gnu.org/licenses/gpl.html

Description

movingAvg is a simple Arduino library for calculating moving averages. It is useful for smoothing sensor readings, etc. For efficiency, the library operates in the integer domain. This means that the calculated moving averages are mathematically approximate. Both data input to the library and the returned moving averages are 16-bit signed integers.

The user specifies the interval (number of data points) for the moving average in the constructor. When the begin() function is called, an array is dynamically allocated to hold the number of data points in the interval. This array is never deallocated, and the user should call begin() only once (for a given movingAvg instance) in setup or other initialization code. Dynamic allocation is used strictly with the intent of creating the proper size array for the user's purposes, and not to free up the memory at a later point. It is strongly recommended that movingAvg objects remain allocated as long as the code is running. Failure to observe these guidelines can result in heap fragmentation, crashes and other undesired behavior.

Constructor

movingAvg(int interval)

Description

Defines a movingAvg object where the average is calculated using interval data points.

Syntax

movingAvg(interval);

Parameters

interval: The number of data points to use when calculating the moving average. (int)

Returns

None.

Example

movingAvg mySensor(10);    // use 10 data points for the moving average

Methods

begin()

Description

Initializes a movingAvg object. Call begin() once and only once for any given movingAvg instance. See comments in the Description section above.

Syntax

begin();

Parameters

None.

Returns

None.

Example

movingAvg mySensor(10);    // use 10 data points for the moving average
mySensor.begin();

reading(int dataPoint)

Description

Adds a new data point to the moving average. Returns the new moving average value. Until the interval array is filled, the average is calculated from those data points already added, i.e. a fewer number of points than defined by the constructor - thanks to Tom H. (Duckie) for this idea!

Syntax

reading(dataPoint);

Parameters

dataPoint: The new data point to be added to the moving average. (int)

Returns

The new moving average value. (int)

Example

int sensorData = analogRead(SENSOR_PIN);
int sensorMovingAvg = mySensor.reading(sensorData);

getAvg()

Description

Returns the current moving average value without adding a new reading.

Syntax

getAvg();

Parameters

None.

Returns

The moving average value. (int)

Example

int sensorMovingAvg = mySensor.getAvg();

getAvg(int nPoints)

Description

Like getAvg() except only uses the most recent nPoints data points to calculate the average. This allows calculation of shorter term and longer term averages. If nPoints is less than one, or larger than the number of points given in the constructor, or larger than the number of data points so far accumulated, then zero is returned.

Syntax

getAvg(nPoints);

Parameters

nPoints: The number of points to use to calculate a shorter-term average. (int)

Returns

The moving average value. (int)

Example

int sensorMovingAvg = mySensor.getAvg(4);

getCount()

Description

Returns the number of data points collected for the moving average, a number between zero and interval. This function can be used to determine if a valid moving average exists. This may be useful, for example, to avoid calling getAvg() before any data points have been added to the moving average. Calling getAvg() before any data points are added causes a divide by zero which will result in invalid data and/or undefined/undesired behavior.

Syntax

getCount();

Parameters

None.

Returns

The number of data points. (int)

Example

int n = mySensor.getCount();

reset()

Description

Restarts the moving average. Zeros the interval array and associated data.

Syntax

reset();

Parameters

None.

Returns

None.

Example

mySensor.reset();

getReadings()

Description

Returns a pointer to the integer array containing the collected data points.

Syntax

getReadings();

Parameters

None.

Returns

Pointer to an integer array. (int*)

Example

movingAvg foo(6);
...
int* myData;
myData = foo.getReadings();
Serial.println(myData[0]);  // first data point
Serial.println(myData[1]);  // second data point
// etc.