-
Notifications
You must be signed in to change notification settings - Fork 3
/
itslive_quiver.m
242 lines (212 loc) · 7.35 KB
/
itslive_quiver.m
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
function h = itslive_quiver(varargin)
% itslive_quiver plots ice velocity arrows on a polar stereographic map.
%
%% Syntax
%
% itslive_quiver
% itslive_quiver('colorspec')
% itslive_quiver(...Name,Value)
% itslive_quiver(...,'density','DensityFactor')
% itslive_quiver(...,'region',region)
% h = itslive_quiver(...)
%
%% Description
%
% itslive_quiver plots a quiver plot on the current map.
%
% itslive_quiver('colorspec') specifies a color of the vectors, like 'r'
% for red.
%
% itslive_quiver(...Name,Value) formats the quiver arrows with any quiver
% properties.
%
% itslive_quiver(...,'density','DensityFactor') specifies the density of
% the arrows. Default DensityFactor is 75, meaning hypot(Nrows,Ncols)=75,
% but if your plot is too crowded you may specify a lower DensityFactor
% (and/or adjust the markersize).
%
% itslive_imagesc(...,'region',region) specifies a region as 'ALA', 'ANT',
% 'CAN', 'GRE', 'HMA', 'ICE', 'PAT', or 'SRA'. Default region is 'ANT'.
%
% h = itslive_quiver(...) returns a handle h of the plotted quiver object.
%
%% Examples
%
% mapzoomps('pine island glacier')
% itslive_quiver
%
% or
% mapzoomps('pine island glacier')
% itslive_quiver('r','density',100)
%
%% Citing this data
% If this function is helpful for you, please cite
%
% Gardner, A. S., M. A. Fahnestock, and T. A. Scambos, 2019 [update to time
% of data download]: ITS_LIVE Regional Glacier and Ice Sheet Surface Velocities.
% Data archived at National Snow and Ice Data Center; doi:10.5067/6II6VW8LLWJ7.
%
% Gardner, A. S., G. Moholdt, T. Scambos, M. Fahnstock, S. Ligtenberg, M. van
% den Broeke, and J. Nilsson, 2018: Increased West Antarctic and unchanged
% East Antarctic ice discharge over the last 7 years, _Cryosphere,_ 12(2):
% 21?547, doi:10.5194/tc-12-521-2018.
%
% Greene, C. A., Gwyther, D. E., & Blankenship, D. D. Antarctic Mapping Tools
% for Matlab. Computers & Geosciences. 104 (2017) pp.151-157.
% http://dx.doi.org/10.1016/j.cageo.2016.08.003
%
%% Author Info
% Chad A. Greene wrote this in May 2019.
%
% See also: itslive_imagesc and itslive_data.
%% Check the presence of a current axes:
ax = axis;
if isequal(ax,[0 1 0 1])
NewMap = true;
else
NewMap = false;
end
tmp = strncmpi(varargin,'region',3);
if any(tmp)
region = varargin{find(tmp)+1};
tmp(find(tmp)+1)=1;
varargin = varargin(~tmp);
else
region = 'ANT'; % antarctica by default
end
%% Load data:
if NewMap
answer = questdlg('The itslive_quiver function works best if you are already zoomed to the extents of interest, however you do not have a map open or zoomed. Loading the entire continent will be slow and the plot won''t be pretty. Continue anyway?',...
'Performance Warning',...
'Go for it anyway','Cancel','Cancel');
if strcmp(answer,'Cancel')
return
end
[vx,x,y] = itslive_data('vx','xy','region',region);
vy = itslive_data('vy','xy','region',region);
else
[vx,x,y] = itslive_data('vx',ax(1:2),ax(3:4),'buffer',10,'xy','region',region); % A little bit of buffer to make the resizing nice.
vy = itslive_data('vy',ax(1:2),ax(3:4),'buffer',10,'xy','region',region);
end
%% Plot things:
hold on
h = quiversc(x,y,vx,vy,varargin{:});
axis xy
daspect([1 1 1])
%% Clean up:
if nargout==0
clear h
end
end
function h = quiversc(x,y,u,v,varargin)
% quiversc scales a dense grid of quiver arrows to comfortably fit in axes
% before plotting them.
%
%% Syntax
%
% quiversc(x,y,u,v)
% quiversc(...,'density',DensityValue)
% quiversc(...,scale)
% quiversc(...,LineSpec)
% quiversc(...,LineSpec,'filled')
% quiversc(...,'Name',Value)
% h = quiversc(...)
%
%% Description
%
% quiversc(x,y,u,v) plots vectors as arrows at the coordinates specified in
% each corresponding pair of elements in x and y. The matrices x, y, u, and
% v must all be the same size and contain corresponding position and velocity
% components. By default, the arrows are scaled to just not overlap, but you
% can scale them to be longer or shorter if you want.
%
% quiversc(...,'density',DensityFactor) specifies density of quiver arrows. The
% DensityFactor defines how many arrows are plotted. Default DensityFactor is
% 50, meaning hypot(Nrows,Ncols)=50, but if your plot is too crowded you may
% specify a lower DensityFactor (and/or adjust the markersize). % CHANGED THIS TO 75 FOR ITSLIVE_QUIVER.
%
% quiversc(...,scale) automatically scales the length of the arrows to fit within
% the grid and then stretches them by the factor scale. scale = 2 doubles their
% relative length, and scale = 0.5 halves the length. Use scale = 0 to plot the
% velocity vectors without automatic scaling. You can also tune the length of
% arrows after they have been drawn by choosing the Plot Edit tool, selecting
% the quiver object, opening the Property Editor, and adjusting the Length slider.
%
% quiversc(...,LineSpec) specifies line style, marker symbol, and color using
% any valid LineSpec. quiversc draws the markers at the origin of the vectors.
%
% quiversc(...,LineSpec,'filled') fills markers specified by LineSpec.
%
% quiversc(...,'Name',Value) specifies property name and property value pairs
% for the quiver objects the function creates.
%
% h = quiversc(...) returns the quiver object handle h.
%
%% Examples
% For examples, type
%
% cdt quiversc
%
%% Author Info
% This function and supporting documentation were written by Chad A. Greene
% of the University of Texas at Austin.
%
% See also: quiver
%% Input parsing:
% Turn vectors into grids:
if all([isvector(x) isvector(y)])
[x,y] = meshgrid(x,y);
end
% Ensure all the dimensions match:
assert(isequal(size(x),size(y),size(u),size(v))==1,'Error: Dimensions of x, y, u, and v must all agree. Check inputs, or use [x,y] = meshgrid(x,y) if necessary.')
% Check for user-defined density:
tmp = strncmpi(varargin,'density',3);
if any(tmp)
density = varargin{find(tmp)+1};
tmp(find(tmp)+1)=1;
varargin = varargin(~tmp);
assert(isscalar(density)==1,'Input error: Density value must be a scalar. Default density is 100.')
else
density = 75; % CHANGED THIS TO 75 FOR ITSLIVE_QUIVER.
end
%% Resize the grids:
% Density is 50 by default, meaning hypot(Nrows,Ncols) will be 50.
InputDensity = hypot(size(x,1),size(x,2));
sc = density/InputDensity; % scaling factor to convert InputDensity to desired density.
if ~isnan(sc)
% First, scale by nearest-neighbor:
xn = imresize(x,sc,'nearest');
yn = imresize(y,sc,'nearest');
un = imresize(u,sc,'nearest');
vn = imresize(v,sc,'nearest');
% For most of the grid we'll use default bicubic though:
x = imresize(x,sc);
y = imresize(y,sc);
u = imresize(u,sc);
v = imresize(v,sc);
% But fill in NaNs with nearest-neighbor results b/c otherwise coastal areas would be decimated:
x(isnan(x)) = xn(isnan(x));
y(isnan(y)) = yn(isnan(y));
u(isnan(u)) = un(isnan(u));
v(isnan(v)) = vn(isnan(v));
end
if true
% Remove every other grid cell in a checkerboard fashion:
% This functionality is turned off, but could easily be added as an
% option in a future release.
% ACTUALLY I TURNED IT ON FOR ITSLIVE_QUIVER.
checker = true(size(x));
checker(1:2:end,1:2:end) = false;
checker(2:2:end,2:2:end) = false;
x(checker) = NaN;
y(checker) = NaN;
u(checker) = NaN;
v(checker) = NaN;
end
%% Plot
h = quiver(x,y,u,v,varargin{:});
%% Clean up:
if nargout==0
clear h
end
end