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import DeveloperError from "./DeveloperError.js";
/**
* An {@link InterpolationAlgorithm} for performing linear interpolation.
*
* @namespace LinearApproximation
*/
const 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);
}
let i;
let y0;
let y1;
const x0 = xTable[0];
const x1 = xTable[1];
//>>includeStart('debug', pragmas.debug);
Iif (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;
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