Mercurial > dive4elements > river
view artifacts/src/main/java/org/dive4elements/river/artifacts/math/Linear.java @ 7471:fff862f4ef76
Experimental caching of datacage recommendations. The respective hook is called a lot and running the datacage over and over again when loading data can be expensive. So the generated recommendations are cached for some time.
Hopefully this improves the overall speed of loading data from the datacage.
author | Sascha L. Teichmann <teichmann@intevation.de> |
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date | Wed, 30 Oct 2013 15:26:21 +0100 |
parents | af13ceeba52a |
children |
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/* Copyright (C) 2011, 2012, 2013 by Bundesanstalt für Gewässerkunde * Software engineering by Intevation GmbH * * This file is Free Software under the GNU AGPL (>=v3) * and comes with ABSOLUTELY NO WARRANTY! Check out the * documentation coming with Dive4Elements River for details. */ package org.dive4elements.river.artifacts.math; public final class Linear implements Function { private double m; private double b; public Linear( double x1, double x2, double y1, double y2 ) { // y1 = m*x1 + b // y2 = m*x2 + b // y2 - y1 = m*(x2 - x1) // m = (y2 - y1)/(x2 - x1) # x2 != x1 // b = y1 - m*x1 if (x1 == x2) { m = 0; b = 0.5*(y1 + y2); } else { m = (y2 - y1)/(x2 - x1); b = y1 - m*x1; } } public static final double linear( double x, double x1, double x2, double y1, double y2 ) { // y1 = m*x1 + b // y2 = m*x2 + b // y2 - y1 = m*(x2 - x1) // m = (y2 - y1)/(x2 - x1) # x2 != x1 // b = y1 - m*x1 if (x1 == x2) { return 0.5*(y1 + y2); } double m = (y2 - y1)/(x2 - x1); double b = y1 - m*x1; return x*m + b; } @Override public double value(double x) { return m*x + b; } public static final double factor(double x, double p1, double p2) { // 0 = m*p1 + b <=> b = -m*p1 // 1 = m*p2 + b // 1 = m*(p2 - p1) // m = 1/(p2 - p1) # p1 != p2 // f(x) = x/(p2-p1) - p1/(p2-p1) <=> (x-p1)/(p2-p1) return p1 == p2 ? 0.0 : (x-p1)/(p2-p1); } public static final double weight(double factor, double a, double b) { //return (1.0-factor)*a + factor*b; return a + factor*(b-a); } public static final void weight( double factor, double [] a, double [] b, double [] c ) { int N = Math.min(Math.min(a.length, b.length), c.length); for (int i = 0; i < N; ++i) { c[i] = weight(factor, a[i], b[i]); } } } // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :