Mercurial > gemma

annotate pkg/common/linear.go @ 4873:8a4c98b80fbd

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Make constraint trigger work in sessions with empty search_path Constraint triggers involving check_sr_in_bn_area() failed when applied in a session with empty search_path, because the used PostGIS function in the public schema was not found. This could prevent restoring values in waterway.sounding_results from a dump created using pg_dump.
author Tom Gottfried <tom@intevation.de>
date Fri, 24 Jan 2020 17:33:12 +0100
parents 18d5461bec5d
children
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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
4558
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14 package common
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15
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16 // Linear constructs a function which maps x1 to y1 and x2 to y2.
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17 // All other values are interpolated linearly.
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18 func Linear(x1, y1, x2, y2 float64) func(float64) float64 {
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19 // f(x1) = y1
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20 // f(x2) = y2
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21 // y1 = x1*a + b <=> b = y1 - x1*a
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22 // y2 = x2*a + b
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23
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24 // y1 - y2 = a*(x1 - x2)
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25 // a = (y1-y2)/(x1 - x2) for x1 != x2
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26
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27 if x1 == x2 {
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28 return func(float64) float64 {
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29 return 0.5 * (y1 + y2)
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30 }
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31 }
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32 a := (y1 - y2) / (x1 - x2)
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33 b := y1 - x1*a
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34 return func(x float64) float64 {
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35 return x*a + b
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36 }
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37 }