You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
84 lines
2.5 KiB
JavaScript
84 lines
2.5 KiB
JavaScript
import defined from "./defined.js";
|
|
import DeveloperError from "./DeveloperError.js";
|
|
|
|
/**
|
|
* An {@link InterpolationAlgorithm} for performing linear interpolation.
|
|
*
|
|
* @namespace LinearApproximation
|
|
*/
|
|
var LinearApproximation = {
|
|
type: "Linear",
|
|
};
|
|
|
|
/**
|
|
* Given the desired degree, returns the number of data points required for interpolation.
|
|
* Since linear interpolation can only generate a first degree polynomial, this function
|
|
* always returns 2.
|
|
* @param {Number} degree The desired degree of interpolation.
|
|
* @returns {Number} This function always returns 2.
|
|
*
|
|
*/
|
|
LinearApproximation.getRequiredDataPoints = function (degree) {
|
|
return 2;
|
|
};
|
|
|
|
/**
|
|
* Interpolates values using linear approximation.
|
|
*
|
|
* @param {Number} x The independent variable for which the dependent variables will be interpolated.
|
|
* @param {Number[]} xTable The array of independent variables to use to interpolate. The values
|
|
* in this array must be in increasing order and the same value must not occur twice in the array.
|
|
* @param {Number[]} yTable The array of dependent variables to use to interpolate. For a set of three
|
|
* dependent values (p,q,w) at time 1 and time 2 this should be as follows: {p1, q1, w1, p2, q2, w2}.
|
|
* @param {Number} yStride The number of dependent variable values in yTable corresponding to
|
|
* each independent variable value in xTable.
|
|
* @param {Number[]} [result] An existing array into which to store the result.
|
|
* @returns {Number[]} The array of interpolated values, or the result parameter if one was provided.
|
|
*/
|
|
LinearApproximation.interpolateOrderZero = function (
|
|
x,
|
|
xTable,
|
|
yTable,
|
|
yStride,
|
|
result
|
|
) {
|
|
//>>includeStart('debug', pragmas.debug);
|
|
if (xTable.length !== 2) {
|
|
throw new DeveloperError(
|
|
"The xTable provided to the linear interpolator must have exactly two elements."
|
|
);
|
|
} else if (yStride <= 0) {
|
|
throw new DeveloperError(
|
|
"There must be at least 1 dependent variable for each independent variable."
|
|
);
|
|
}
|
|
//>>includeEnd('debug');
|
|
|
|
if (!defined(result)) {
|
|
result = new Array(yStride);
|
|
}
|
|
|
|
var i;
|
|
var y0;
|
|
var y1;
|
|
var x0 = xTable[0];
|
|
var x1 = xTable[1];
|
|
|
|
//>>includeStart('debug', pragmas.debug);
|
|
if (x0 === x1) {
|
|
throw new DeveloperError(
|
|
"Divide by zero error: xTable[0] and xTable[1] are equal"
|
|
);
|
|
}
|
|
//>>includeEnd('debug');
|
|
|
|
for (i = 0; i < yStride; i++) {
|
|
y0 = yTable[i];
|
|
y1 = yTable[i + yStride];
|
|
result[i] = ((y1 - y0) * x + x1 * y0 - x0 * y1) / (x1 - x0);
|
|
}
|
|
|
|
return result;
|
|
};
|
|
export default LinearApproximation;
|