FRC Interpolation Solver

Calculates a line based on a given set of points to allow interpolation and extrapolation of the data. The data can also be graphed. For usage in the First Robotics Competition.

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Implementation

Create an InterpolationSolver object with your X and Y data, and specify the polynomial degree. Most applications will be best with a linear line (degree 1) or quadratic line (degree 2)

// Imports
import frc.robot.InterpolationSolver.InterpolationSolver;

double[] x = {1, 2, 3, 4, 5}; // X Points
double[] y = {1, 4, 10, 15, 23}; // Y Points

InterpolationSolver solver = new InterpolationSolver(x, y, 2);

For better code readability, you can also specify the degree like this:

// Imports
import frc.robot.InterpolationSolver.InterpolationSolver.LineType; // Add this import

...

InterpolationSolver solver = new InterpolationSolver(x, y, LineType.QUADRATIC);

Adding Range

A minimum and/or maximum value can be specified in the constructor

InterpolationSolver solver = new InterpolationSolver(x, y, 2, 3.0, 20.0); // minimum value: 3.0, maximum value: 20.0

Also, you can specify only one by leaving one NaN

InterpolationSolver solver = new InterpolationSolver(x, y, 2, 3.0, Double.NaN); // minimum value: 3.0, no maximum value

The range is also sometimes referred to as 'bounds'.

Solving

The solve method takes a double value for X, and returns the Y prediction. If the graph is enabled, it will also update it.

Double y = solver.solve(10.0);

Get Equation

For debugging and testing purposes, it is sometimes needed to get the equation being used. The toString() method will return this, along with the coefficent of determination (r^2)

String equation = solver.toString();

Graphing

To show the graph as a camera stream, first you need to create a GraphingConfig object. If you leave this blank, default values will be used.

// Imports
import frc.robot.InterpolationSolver.GraphingConfig;

GraphingConfig config = new GraphingConfig();

Then, run the initGraph() method, with the name to stream the graph under. If no GraphingConfig object is provided, the defaut will be used.

solver.initGraph("Graph Name", config);
// OR
solver.initGraph("Graph Name");

Changing the Graph Theme

3 built-in themes are added, to match Shuffleboard's built-in themes, Light, Dark, and Midnight. Specifying one of them in the constructor of a GraphingConfig object will use these defaults.

// Imports
import frc.robot.InterpolationSolver.GraphingConfig.GraphTheme;

// Light Theme
GraphingConfig config = new GraphingConfig(GraphTheme.LIGHT); // (this is default)

// Dark Theme
GraphingConfig config = new GraphingConfig(GraphTheme.DARK);

// Midnight Theme
GraphingConfig config = new GraphingConfig(GraphTheme.MIDNIGHT);

Further Graph Customization

Individual values of the GraphingConfig object can be changed. A complete list is below:

Property Name*	Value Type	Description
background	Color	The background color of the graph
gridLineColor	Color	The color of the graph's grid lines
labelColor	Color	The color of the labels along the graph's X and Y axis
lineColor	Color	The color of the line, as well as each of the points on the line
pointRadius	int	The radius of each point on the line (input data), as well as each prediction
checkerColor	Color	The color of the checker line, which shows the position of each prediction
equationColor	Color	The color of the text of the equation at the bottom
boundsColor	Color	The color of the upper and lower range on the graph
fps	int	The number of frames per second that the graph will be streamed at

*case sensitive
import Color object from frc.robot.InterpolationSolver.Color

Getting the CvSource object

While graphing, the CvSource object can be accessed, to push to Shuffleboard or other Driver Station dashboards.

CvSrouce graph = solver.getCvSource();