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154 lines
3.5 KiB
Lua
154 lines
3.5 KiB
Lua
--[[ $Id: x19.lua 10293 2009-08-19 07:57:43Z smekal $
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Illustrates backdrop plotting of world, US maps.
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Contributed by Wesley Ebisuzaki.
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Copyright (C) 2008 Werner Smekal
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This file is part of PLplot.
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PLplot is free software you can redistribute it and/or modify
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it under the terms of the GNU General Library Public License as published
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by the Free Software Foundation either version 2 of the License, or
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(at your option) any later version.
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PLplot is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Library General Public License for more details.
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You should have received a copy of the GNU Library General Public License
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along with PLplot if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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--]]
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-- initialise Lua bindings for PLplot examples.
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dofile("plplot_examples.lua")
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--------------------------------------------------------------------------
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-- mapform19
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--
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-- Defines specific coordinate transformation for example 19.
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-- Not to be confused with mapform in src/plmap.c.
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-- x[], y[] are the coordinates to be plotted.
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--------------------------------------------------------------------------
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function mapform19(n, x, y)
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for i = 1, n do
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radius = 90 - y[i]
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xp = radius * math.cos(x[i] * math.pi / 180)
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yp = radius * math.sin(x[i] * math.pi / 180)
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x[i] = xp
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y[i] = yp
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end
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return x, y
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end
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-- "Normalize" longitude values so that they always fall between
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-- -180.0 and 180.0
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function normalize_longitude(lon)
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if lon>=-180 and lon<=180 then
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return lon;
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else
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times = math.floor((math.abs(lon)+180)/360)
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if lon<0 then
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return lon+360*times
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else
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return lon-360*times
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end
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end
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end
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-- A custom axis labeling function for longitudes and latitudes.
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function geolocation_labeler(axis, value)
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if axis==pl.PL_Y_AXIS then
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label_val = value
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if label_val>0 then
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direction_label = " N"
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else
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if label_val<0 then
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direction_label = " S"
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else
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direction_label = "Eq"
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end
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end
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else
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if axis==pl.PL_X_AXIS then
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label_val = normalize_longitude(value);
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if label_val>0 then
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direction_label = " E"
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else
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if label_val<0 then
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direction_label = " W"
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else
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direction_label = ""
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end
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end
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end
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end
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if axis==pl.PL_Y_AXIS and value==0 then
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-- A special case for the equator
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label = direction_label
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else
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label = math.abs(label_val) .. direction_label
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end
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return label
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end
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--------------------------------------------------------------------------
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-- main
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--
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-- Shows two views of the world map.
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--------------------------------------------------------------------------
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-- Parse and process command line arguments
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pl.parseopts(arg, pl.PL_PARSE_FULL)
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-- Longitude (x) and latitude (y)
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miny = -70
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maxy = 80
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pl.init()
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-- Cartesian plots
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-- Most of world
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minx = 190
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maxx = 190+360
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-- Setup a custom latitude and longitude-based scaling function.
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pl.slabelfunc("geolocation_labeler");
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pl.col0(1)
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pl.env(minx, maxx, miny, maxy, 1, 70)
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pl.map(nil, "usaglobe", minx, maxx, miny, maxy)
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-- The Americas
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minx = 190
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maxx = 340
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pl.col0(1)
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pl.env(minx, maxx, miny, maxy, 1, 70)
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pl.map(nil, "usaglobe", minx, maxx, miny, maxy)
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-- Clear the labeling function
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pl.slabelfunc(nil);
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-- Polar, Northern hemisphere
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minx = 0
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maxx = 360
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pl.env(-75., 75., -75., 75., 1, -1)
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pl.map("mapform19", "globe", minx, maxx, miny, maxy)
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pl.lsty(2)
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pl.meridians("mapform19", 10, 10, 0, 360, -10, 80)
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pl.plend()
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