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Moved linear interpolation to common package for re-use.
author Sascha L. Teichmann <sascha.teichmann@intevation.de>
date Wed, 02 Oct 2019 11:00:09 +0200
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children 18d5461bec5d
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4558
07f632cd2625 Moved linear interpolation to common package for re-use.
Sascha L. Teichmann <sascha.teichmann@intevation.de>
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1 // This is Free Software under GNU Affero General Public License v >= 3.0
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2 // without warranty, see README.md and license for details.
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3 //
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4 // SPDX-License-Identifier: AGPL-3.0-or-later
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5 // License-Filename: LICENSES/AGPL-3.0.txt
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6 //
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7 // Copyright (C) 2019 by via donau
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8 // – Österreichische Wasserstraßen-Gesellschaft mbH
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9 // Software engineering by Intevation GmbH
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10 //
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11 // Author(s):
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12 // * Sascha L. Teichmann <sascha.teichmann@intevation.de>
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13 package common
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14
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15 // Linear constructs a function which maps x1 to y1 and x2 to y2.
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16 // All other values are interpolated linearly.
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17 func Linear(x1, y1, x2, y2 float64) func(float64) float64 {
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18 // f(x1) = y1
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19 // f(x2) = y2
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20 // y1 = x1*a + b <=> b = y1 - x1*a
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21 // y2 = x2*a + b
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22
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23 // y1 - y2 = a*(x1 - x2)
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24 // a = (y1-y2)/(x1 - x2) for x1 != x2
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25
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26 if x1 == x2 {
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27 return func(float64) float64 {
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28 return 0.5 * (y1 + y2)
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29 }
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30 }
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31 a := (y1 - y2) / (x1 - x2)
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32 b := y1 - x1*a
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33 return func(x float64) float64 {
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34 return x*a + b
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35 }
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36 }