/*
 * Copyright (c) 2016 Jacob Rachiele
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
 * and associated documentation files (the "Software"), to deal in the Software without restriction
 * including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense
 * and/or sell copies of the Software, and to permit persons to whom the Software is furnished to
 * do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or
 * substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 * USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * Contributors:
 *
 * Jacob Rachiele
 */
package math.polynomial.interpolation;

/**
 * Linear interpolation of two known points.
 */
public final class LinearInterpolation {

    private final double a0;
    private final double a1;

    public LinearInterpolation(final double x0, final double x1, final double f0, final double f1) {
        if (x0 == x1) {
            throw new IllegalArgumentException("x0 and x1 must be distinct points, but both were equal to: " + x1);
        }
        this.a0 = (x1 * f0 - f1 * x0) / (x1 - x0);
        this.a1 = (f1 - a0) / x1;
    }

    public double a0() {
        return a0;
    }

    public double a1() {
        return a1;
    }

}

@@ -1607,29 +1607,19 @@
 is.a
-0
+1
  = (
-x1 * f0 - f1 * x
+f1 - f
 0) /
@@ -1648,23 +1648,21 @@
 is.a
-1
+0
  = 
-(
 f1 - a
-0) /
+1 *
  x1;

Use simpler formula for linear interpolation