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james ryan
2025-03-24 00:43:09 -04:00
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57
lessons/lesson03/matlab_logo.m Normal file
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%% Creating the MATLAB logo
% from https://www.mathworks.com/help/matlab/visualize/creating-the-matlab-logo.html
% Copyright (C) 2014 Mathworks Inc.
close all; clear; clc;
%% Create the surface
L = 160*membrane(1,100);
%% Create the figure and axes
f = figure;
ax = axes;
s = surface(L);
s.EdgeColor = 'none';
view(3)
%% Adjust axis limits
ax.XLim = [1 201];
ax.YLim = [1 201];
ax.ZLim = [-53.4 160];
%% Adjust the camera position
ax.CameraPosition = [-145.5 -229.7 283.6];
ax.CameraTarget = [77.4 60.2 63.9];
ax.CameraUpVector = [0 0 1];
ax.CameraViewAngle = 36.7;
%% Adjust the position of the x, y, z axes themselves
ax.Position = [0 0 1 1];
ax.DataAspectRatio = [1 1 .9];
%% Add some light
l1 = light;
l1.Position = [160 400 80];
l1.Style = 'local';
l1.Color = [0 0.8 0.8];
l2 = light;
l2.Position = [.5 -1 .4];
l2.Color = [0.8 0.8 0];
%% Change the surface color
s.FaceColor = [0.9 0.2 0.2];
%% Adjust lighting algorithm
s.FaceLighting = 'gouraud';
s.AmbientStrength = 0.3;
s.DiffuseStrength = 0.6;
s.BackFaceLighting = 'lit';
s.SpecularStrength = 1;
s.SpecularColorReflectance = 1;
s.SpecularExponent = 7;
%% Remove background
axis off
f.Color = 'black';

711
lessons/lesson03/octave-log.txt Normal file
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octave:2>
octave:2>
octave:2>
octave:16>
y2 = x.^2;^[[201~octave:16>
octave:16>
octave:16>
octave:16>
octave:16> x = -10:0.1:10;
y = x.^3;
y2 = x.^2;
octave:19> size(y)
ans =
1 201
octave:20> size(x)
ans =
1 201
octave:21> plot(x, y)
octave:22> plot(x, y2)
octave:23> hold on
octave:24> plot(x, y)
octave:25> figure
octave:26> plot(x, y)
octave:27> close all
octave:28> figure
octave:29> plot(x, y)
octave:30> xlabel('x axis')
octave:31> ylabel('y axis')
octave:32> ylabel('y axis! yay!')
octave:33> ylabel('y axis! yay! more letters')
octave:34> title('a plot of a cubic')
octave:35> grid on
octave:36> legend('x^3')
octave:37> hold on
octave:38> close all
octave:39>
^[[201~octave:39>
octave:39>
octave:39>
octave:39>
octave:39> hold on; % plotting more than 1 plot on 1 figure rather than overwriting
plot(x, y, 'DisplayName', 'x^3');
plot(x, y2, 'DisplayName', 'x^2');
hold off;
xlabel 'x axis';
ylabel 'y axis';
title 'Example 1';
xlim([-10 10]);
ylim([-10 10]);
% axis([-10 10 -10 10]);
grid on;
legend show; % 'DisplayName does thisi
octave:50> close all
octave:51> help axis
'axis' is a function from the file /usr/share/octave/7.3.0/m/plot/appearance/axis.m
-- axis ()
-- axis ([X_LO X_HI])
-- axis ([X_LO X_HI Y_LO Y_HI])
-- axis ([X_LO X_HI Y_LO Y_HI Z_LO Z_HI])
-- axis ([X_LO X_HI Y_LO Y_HI Z_LO Z_HI C_LO C_HI])
-- axis (OPTION)
-- axis (OPTION1, OPTION2, ...)
-- axis (HAX, ...)
-- LIMITS = axis ()
Set axis limits and appearance.
The argument LIMITS should be a 2-, 4-, 6-, or 8-element vector.
The first and second elements specify the lower and upper limits
for the x-axis. The third and fourth specify the limits for the
y-axis, the fifth and sixth specify the limits for the z-axis, and
the seventh and eighth specify the limits for the color axis. The
special values '-Inf' and 'Inf' may be used to indicate that the
limit should be automatically computed based on the data in the
axes.
Without any arguments, 'axis' turns autoscaling on.
With one output argument, 'LIMITS = axis' returns the current axis
limits.
The vector argument specifying limits is optional, and additional
string arguments may be used to specify various axis properties.
The following options control the aspect ratio of the axes.
"equal"
Force x-axis unit distance to equal y-axis (and z-axis) unit
distance.
"square"
Force a square axis aspect ratio.
"vis3d"
Set aspect ratio modes ("DataAspectRatio",
"PlotBoxAspectRatio") to "manual" for rotation without
stretching.
"normal"
"fill"
Restore default automatically computed aspect ratios.
The following options control the way axis limits are interpreted.
"auto"
"auto[xyz]"
"auto [xyz]"
Set nice auto-computed limits around the data for all axes, or
only the specified axes.
"manual"
Fix the current axes limits.
"tight"
Fix axes to the limits of the data.
"image"
Equivalent to "tight" and "equal".
The following options affect the appearance of tick marks.
"tic"
"tic[xyz]"
"tic [xyz]"
Turn tick marks on for all axes, or turn them on for the
specified axes and off for the remainder.
"label"
"label[xyz]"
"label [xyz]"
Turn tick labels on for all axes, or turn them on for the
specified axes and off for the remainder.
"nolabel"
Turn tick labels off for all axes.
Note: If there are no tick marks for an axes then there can be no
labels.
The following options affect the direction of increasing values on
the axes.
"xy"
Default y-axis, larger values are near the top.
"ij"
Reverse y-axis, smaller values are near the top.
The following options affects the visibility of the axes.
"on"
Make the axes visible.
"off"
Hide the axes.
If the first argument HAX is an axes handle, then operate on this
axes rather than the current axes returned by 'gca'.
Example 1: set X/Y limits and force a square aspect ratio
axis ([1, 2, 3, 4], "square");
Example 2: enable tick marks on all axes, enable tick mark labels
only on the y-axis
axis ("tic", "labely");
See also: xlim, ylim, zlim, caxis, daspect, pbaspect, box, grid.
Additional help for built-in functions and operators is
available in the online version of the manual. Use the command
'doc <topic>' to search the manual index.
Help and information about Octave is also available on the WWW
at https://www.octave.org and via the help@octave.org
mailing list.
octave:52>
d2 = cos(t);^[[201~octave:52>
octave:52>
octave:52>
octave:52>
octave:52> t = 0:.1:10;
d1 = sin(t);
d2 = cos(t);
octave:55> figure
octave:56>
^[[200~hold on;
plot(t, d1);
plot(t, d2);
hold off;^[[201~octave:56>
octave:56>
octave:56>
octave:56>
octave:56> hold on;
plot(t, d1);
plot(t, d2);
hold off;
octave:60>
^[[200~title 'Trig Functions';^[[201~octave:60>
octave:60>
octave:60>
octave:60>
octave:60> title 'Trig Functions';
octave:61>
^[[200~xlabel 'time (\mu)s';^[[201~octave:61>
octave:61>
octave:61>
octave:61>
octave:61> xlabel('time (\mu)s');
octave:62> ylabel('voltage')
octave:63> legend('sin', 'cos')
octave:64> close all
octave:65> figure
octave:66>
octave:66>
octave:66>
octave:66>
octave:66>
octave:66> plot(t, d1, 'b-.', t, d2, 'rp');
octave:67>
^[[200~title 'Trig Functions';
xlabel 'time ($\mu$s)' Interpreter latex
ylabel voltage;
legend('sin', 'cos');
xticks(0:pi/2:10);
xticklabels({'0', '\pi/2', '\pi', '3\pi/2', '2\pi', '5\pi/2', '3\pi'});^[[201~octave:6
7>
octave:67>
octave:67>
octave:67>
octave:67> title 'Trig Functions';
xlabel 'time ($\mu$s)' Interpreter latex
ylabel voltage;
legend('sin', 'cos');
xticks(0:pi/2:10);
xticklabels({'0', '\pi/2', '\pi', '3\pi/2', '2\pi', '5\pi/2', '3\pi'});
sh: 1: dvipng: not found
warning: latex_renderer: a run-time test failed and the 'latex' interpreter has been d
isabled.
warning: called from
__axis_label__ at line 36 column 6
xlabel at line 59 column 8
octave:73> title 'Trig Functions';
xlabel 'time ($\mu$s)' Interpreter latex
ylabel voltage;
legend('sin', 'cos');
xticks(0:pi/2:10);
xticklabels({'0', '\pi/2', '\pi', '3\pi/2',
octave:73>
^[[200~xticks(0:pi/2:10);^[[201~octave:73>
octave:73>
octave:73>
octave:73>
octave:73> xticks(0:pi/2:10);
octave:74>
^[[200~xticklabels({'0', '\pi/2', '\pi', '3\pi/2', '2\pi', '5\pi/2', '3\pi'});^[[201~o
ctave:74>
octave:74>
octave:74>
octave:74>
octave:74> xticklabels({'0', '\pi/2', '\pi', '3\pi/2', '2\pi', '5\pi/2', '3\pi'});
octave:75> close all
octave:76> figure
octave:77> subplot(2, 1, 1)
octave:78>
^[[200~octave:75> close all^[[201~octave:78>
octave:78>
octave:78>
octave:78>
octave:78> octave:75> close all
octave:78> figure
octave:79> subplot(2, 1, 1)
octave:80> plot(t, d1)
octave:81> hold on
octave:82> plot(t, d2)
octave:83> title('an ordinary plot')
octave:84> subplot(2, 1, 2)
octave:85>
octave:85>
octave:85>
octave:85>
octave:85>
octave:85> plot(t, d1, 'b-.', t, d2, 'rp');
title 'Customized plot';
octave:87> close all
octave:88> figure
octave:89> stem(t, d1)
octave:90> hold on
octave:91> scatter(t, d2)
octave:92> close all
octave:93>
^[[200~t = linspace(0,10*pi);^[[201~octave:93>
octave:93>
octave:93>
octave:93>
octave:93> t = linspace(0,10*pi);
octave:94> figure
octave:95> plot3(sin(t), cos(t), t)
octave:96> zlabel('t')
octave:97> zlabel('tttttttttttttttttttttttttttttttttttt')
octave:98> title('a helix! in space!')
octave:99> text(0, 0, 0, 'origin')
octave:100> close all
octave:101>
^[[200~a1 = -2:0.25:2;
b1 = a1;
[A1, B1] = meshgrid(a1);
F = A1.*exp(-A1.^2-B1.^2);^[[201~octave:101>
octave:101>
octave:101>
octave:101>
octave:101> a1 = -2:0.25:2;
b1 = a1;
[A1, B1] = meshgrid(a1);
F = A1.*exp(-A1.^2-B1.^2);
octave:105> A1
A1 =
Columns 1 through 9:
-2.0000 -1.7500 -1.5000 -1.2500 -1.0000 -0.7500 -0.5000 -0.2500 0
-2.0000 -1.7500 -1.5000 -1.2500 -1.0000 -0.7500 -0.5000 -0.2500 0
-2.0000 -1.7500 -1.5000 -1.2500 -1.0000 -0.7500 -0.5000 -0.2500 0
-2.0000 -1.7500 -1.5000 -1.2500 -1.0000 -0.7500 -0.5000 -0.2500 0
-2.0000 -1.7500 -1.5000 -1.2500 -1.0000 -0.7500 -0.5000 -0.2500 0
-2.0000 -1.7500 -1.5000 -1.2500 -1.0000 -0.7500 -0.5000 -0.2500 0
-2.0000 -1.7500 -1.5000 -1.2500 -1.0000 -0.7500 -0.5000 -0.2500 0
-2.0000 -1.7500 -1.5000 -1.2500 -1.0000 -0.7500 -0.5000 -0.2500 0
-2.0000 -1.7500 -1.5000 -1.2500 -1.0000 -0.7500 -0.5000 -0.2500 0
-2.0000 -1.7500 -1.5000 -1.2500 -1.0000 -0.7500 -0.5000 -0.2500 0
-2.0000 -1.7500 -1.5000 -1.2500 -1.0000 -0.7500 -0.5000 -0.2500 0
-2.0000 -1.7500 -1.5000 -1.2500 -1.0000 -0.7500 -0.5000 -0.2500 0
-2.0000 -1.7500 -1.5000 -1.2500 -1.0000 -0.7500 -0.5000 -0.2500 0
-2.0000 -1.7500 -1.5000 -1.2500 -1.0000 -0.7500 -0.5000 -0.2500 0
-2.0000 -1.7500 -1.5000 -1.2500 -1.0000 -0.7500 -0.5000 -0.2500 0
-2.0000 -1.7500 -1.5000 -1.2500 -1.0000 -0.7500 -0.5000 -0.2500 0
-2.0000 -1.7500 -1.5000 -1.2500 -1.0000 -0.7500 -0.5000 -0.2500 0
Columns 10 through 17:
0.2500 0.5000 0.7500 1.0000 1.2500 1.5000 1.7500 2.0000
0.2500 0.5000 0.7500 1.0000 1.2500 1.5000 1.7500 2.0000
0.2500 0.5000 0.7500 1.0000 1.2500 1.5000 1.7500 2.0000
0.2500 0.5000 0.7500 1.0000 1.2500 1.5000 1.7500 2.0000
0.2500 0.5000 0.7500 1.0000 1.2500 1.5000 1.7500 2.0000
0.2500 0.5000 0.7500 1.0000 1.2500 1.5000 1.7500 2.0000
0.2500 0.5000 0.7500 1.0000 1.2500 1.5000 1.7500 2.0000
0.2500 0.5000 0.7500 1.0000 1.2500 1.5000 1.7500 2.0000
0.2500 0.5000 0.7500 1.0000 1.2500 1.5000 1.7500 2.0000
0.2500 0.5000 0.7500 1.0000 1.2500 1.5000 1.7500 2.0000
0.2500 0.5000 0.7500 1.0000 1.2500 1.5000 1.7500 2.0000
0.2500 0.5000 0.7500 1.0000 1.2500 1.5000 1.7500 2.0000
0.2500 0.5000 0.7500 1.0000 1.2500 1.5000 1.7500 2.0000
0.2500 0.5000 0.7500 1.0000 1.2500 1.5000 1.7500 2.0000
0.2500 0.5000 0.7500 1.0000 1.2500 1.5000 1.7500 2.0000
0.2500 0.5000 0.7500 1.0000 1.2500 1.5000 1.7500 2.0000
0.2500 0.5000 0.7500 1.0000 1.2500 1.5000 1.7500 2.0000
octave:106> B1
B1 =
Columns 1 through 9:
-2.0000 -2.0000 -2.0000 -2.0000 -2.0000 -2.0000 -2.0000 -2.0000 -2.0000
-1.7500 -1.7500 -1.7500 -1.7500 -1.7500 -1.7500 -1.7500 -1.7500 -1.7500
-1.5000 -1.5000 -1.5000 -1.5000 -1.5000 -1.5000 -1.5000 -1.5000 -1.5000
-1.2500 -1.2500 -1.2500 -1.2500 -1.2500 -1.2500 -1.2500 -1.2500 -1.2500
-1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000
-0.7500 -0.7500 -0.7500 -0.7500 -0.7500 -0.7500 -0.7500 -0.7500 -0.7500
-0.5000 -0.5000 -0.5000 -0.5000 -0.5000 -0.5000 -0.5000 -0.5000 -0.5000
-0.2500 -0.2500 -0.2500 -0.2500 -0.2500 -0.2500 -0.2500 -0.2500 -0.2500
0 0 0 0 0 0 0 0 0
0.2500 0.2500 0.2500 0.2500 0.2500 0.2500 0.2500 0.2500 0.2500
0.5000 0.5000 0.5000 0.5000 0.5000 0.5000 0.5000 0.5000 0.5000
0.7500 0.7500 0.7500 0.7500 0.7500 0.7500 0.7500 0.7500 0.7500
1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000
1.2500 1.2500 1.2500 1.2500 1.2500 1.2500 1.2500 1.2500 1.2500
1.5000 1.5000 1.5000 1.5000 1.5000 1.5000 1.5000 1.5000 1.5000
1.7500 1.7500 1.7500 1.7500 1.7500 1.7500 1.7500 1.7500 1.7500
2.0000 2.0000 2.0000 2.0000 2.0000 2.0000 2.0000 2.0000 2.0000
Columns 10 through 17:
-2.0000 -2.0000 -2.0000 -2.0000 -2.0000 -2.0000 -2.0000 -2.0000
-1.7500 -1.7500 -1.7500 -1.7500 -1.7500 -1.7500 -1.7500 -1.7500
-1.5000 -1.5000 -1.5000 -1.5000 -1.5000 -1.5000 -1.5000 -1.5000
-1.2500 -1.2500 -1.2500 -1.2500 -1.2500 -1.2500 -1.2500 -1.2500
-1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000
-0.7500 -0.7500 -0.7500 -0.7500 -0.7500 -0.7500 -0.7500 -0.7500
-0.5000 -0.5000 -0.5000 -0.5000 -0.5000 -0.5000 -0.5000 -0.5000
-0.2500 -0.2500 -0.2500 -0.2500 -0.2500 -0.2500 -0.2500 -0.2500
0 0 0 0 0 0 0 0
0.2500 0.2500 0.2500 0.2500 0.2500 0.2500 0.2500 0.2500
0.5000 0.5000 0.5000 0.5000 0.5000 0.5000 0.5000 0.5000
0.7500 0.7500 0.7500 0.7500 0.7500 0.7500 0.7500 0.7500
1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000
1.2500 1.2500 1.2500 1.2500 1.2500 1.2500 1.2500 1.2500
1.5000 1.5000 1.5000 1.5000 1.5000 1.5000 1.5000 1.5000
1.7500 1.7500 1.7500 1.7500 1.7500 1.7500 1.7500 1.7500
2.0000 2.0000 2.0000 2.0000 2.0000 2.0000 2.0000 2.0000
octave:107> F
F =
Columns 1 through 9:
-0.0007 -0.0015 -0.0029 -0.0048 -0.0067 -0.0078 -0.0071 -0.0043 0
-0.0017 -0.0038 -0.0074 -0.0123 -0.0172 -0.0200 -0.0182 -0.0110 0
-0.0039 -0.0086 -0.0167 -0.0276 -0.0388 -0.0450 -0.0410 -0.0248 0
-0.0077 -0.0172 -0.0331 -0.0549 -0.0771 -0.0896 -0.0816 -0.0492 0
-0.0135 -0.0301 -0.0582 -0.0964 -0.1353 -0.1572 -0.1433 -0.0864 0
-0.0209 -0.0466 -0.0901 -0.1493 -0.2096 -0.2435 -0.2219 -0.1338 0
-0.0285 -0.0637 -0.1231 -0.2041 -0.2865 -0.3328 -0.3033 -0.1829 0
-0.0344 -0.0769 -0.1485 -0.2461 -0.3456 -0.4014 -0.3658 -0.2206 0
-0.0366 -0.0818 -0.1581 -0.2620 -0.3679 -0.4273 -0.3894 -0.2349 0
-0.0344 -0.0769 -0.1485 -0.2461 -0.3456 -0.4014 -0.3658 -0.2206 0
-0.0285 -0.0637 -0.1231 -0.2041 -0.2865 -0.3328 -0.3033 -0.1829 0
-0.0209 -0.0466 -0.0901 -0.1493 -0.2096 -0.2435 -0.2219 -0.1338 0
-0.0135 -0.0301 -0.0582 -0.0964 -0.1353 -0.1572 -0.1433 -0.0864 0
-0.0077 -0.0172 -0.0331 -0.0549 -0.0771 -0.0896 -0.0816 -0.0492 0
-0.0039 -0.0086 -0.0167 -0.0276 -0.0388 -0.0450 -0.0410 -0.0248 0
-0.0017 -0.0038 -0.0074 -0.0123 -0.0172 -0.0200 -0.0182 -0.0110 0
-0.0007 -0.0015 -0.0029 -0.0048 -0.0067 -0.0078 -0.0071 -0.0043 0
Columns 10 through 17:
0.0043 0.0071 0.0078 0.0067 0.0048 0.0029 0.0015 0.0007
0.0110 0.0182 0.0200 0.0172 0.0123 0.0074 0.0038 0.0017
0.0248 0.0410 0.0450 0.0388 0.0276 0.0167 0.0086 0.0039
0.0492 0.0816 0.0896 0.0771 0.0549 0.0331 0.0172 0.0077
0.0864 0.1433 0.1572 0.1353 0.0964 0.0582 0.0301 0.0135
0.1338 0.2219 0.2435 0.2096 0.1493 0.0901 0.0466 0.0209
0.1829 0.3033 0.3328 0.2865 0.2041 0.1231 0.0637 0.0285
0.2206 0.3658 0.4014 0.3456 0.2461 0.1485 0.0769 0.0344
0.2349 0.3894 0.4273 0.3679 0.2620 0.1581 0.0818 0.0366
0.2206 0.3658 0.4014 0.3456 0.2461 0.1485 0.0769 0.0344
0.1829 0.3033 0.3328 0.2865 0.2041 0.1231 0.0637 0.0285
0.1338 0.2219 0.2435 0.2096 0.1493 0.0901 0.0466 0.0209
0.0864 0.1433 0.1572 0.1353 0.0964 0.0582 0.0301 0.0135
0.0492 0.0816 0.0896 0.0771 0.0549 0.0331 0.0172 0.0077
0.0248 0.0410 0.0450 0.0388 0.0276 0.0167 0.0086 0.0039
0.0110 0.0182 0.0200 0.0172 0.0123 0.0074 0.0038 0.0017
0.0043 0.0071 0.0078 0.0067 0.0048 0.0029 0.0015 0.0007
octave:108> figure
octave:109> surf(A1, B1, F)
octave:110> figure
octave:111> mesh(A1, B1, F)
octave:112> close all
octave:113> help quiver
'quiver' is a function from the file /usr/share/octave/7.3.0/m/plot/draw/quiver.m
-- quiver (U, V)
-- quiver (X, Y, U, V)
-- quiver (..., S)
-- quiver (..., STYLE)
-- quiver (..., "filled")
-- quiver (HAX, ...)
-- H = quiver (...)
Plot a 2-D vector field with arrows.
Plot the (U, V) components of a vector field at the grid points
defined by (X, Y). If the grid is uniform then X and Y can be
specified as vectors and 'meshgrid' is used to create the 2-D grid.
If X and Y are not given they are assumed to be '(1:M, 1:N)' where
'[M, N] = size (U)'.
The optional input S is a scalar defining a scaling factor to use
for the arrows of the field relative to the mesh spacing. A value
of 1.0 will result in the longest vector exactly filling one grid
square. A value of 0 disables all scaling. The default value is
0.9.
The style to use for the plot can be defined with a line style
STYLE of the same format as the 'plot' command. If a marker is
specified then the markers are drawn at the origin of the vectors
(which are the grid points defined by X and Y). When a marker is
specified, the arrowhead is not drawn. If the argument "filled" is
given then the markers are filled.
If the first argument HAX is an axes handle, then plot into this
axes, rather than the current axes returned by 'gca'.
The optional return value H is a graphics handle to a quiver
object. A quiver object regroups the components of the quiver plot
(body, arrow, and marker), and allows them to be changed together.
Example:
[x, y] = meshgrid (1:2:20);
h = quiver (x, y, sin (2*pi*x/10), sin (2*pi*y/10));
set (h, "maxheadsize", 0.33);
See also: quiver3, compass, feather, plot.
Additional help for built-in functions and operators is
available in the online version of the manual. Use the command
'doc <topic>' to search the manual index.
Help and information about Octave is also available on the WWW
at https://www.octave.org and via the help@octave.org
mailing list.
octave:114> help quiver3
'quiver3' is a function from the file /usr/share/octave/7.3.0/m/plot/draw/quiver3.m
-- quiver3 (X, Y, Z, U, V, W)
-- quiver3 (Z, U, V, W)
-- quiver3 (..., S)
-- quiver3 (..., STYLE)
-- quiver3 (..., "filled")
-- quiver3 (HAX, ...)
-- H = quiver3 (...)
Plot a 3-D vector field with arrows.
Plot the (U, V, W) components of a vector field at the grid points
defined by (X, Y, Z). If the grid is uniform then X, Y, and Z can
be specified as vectors and 'meshgrid' is used to create the 3-D
grid.
If X and Y are not given they are assumed to be '(1:M, 1:N)' where
'[M, N] = size (U)'.
The optional input S is a scalar defining a scaling factor to use
for the arrows of the field relative to the mesh spacing. A value
of 1.0 will result in the longest vector exactly filling one grid
cube. A value of 0 disables all scaling. The default value is
0.9.
The style to use for the plot can be defined with a line style
STYLE of the same format as the 'plot' command. If a marker is
specified then the markers are drawn at the origin of the vectors
(which are the grid points defined by X, Y, Z). When a marker is
specified, the arrowhead is not drawn. If the argument "filled" is
given then the markers are filled.
If the first argument HAX is an axes handle, then plot into this
axes, rather than the current axes returned by 'gca'.
The optional return value H is a graphics handle to a quiver
object. A quiver object regroups the components of the quiver plot
(body, arrow, and marker), and allows them to be changed together.
[x, y, z] = peaks (25);
surf (x, y, z);
hold on;
[u, v, w] = surfnorm (x, y, z / 10);
h = quiver3 (x, y, z, u, v, w);
set (h, "maxheadsize", 0.33);
See also: quiver, compass, feather, plot.
Additional help for built-in functions and operators is
available in the online version of the manual. Use the command
'doc <topic>' to search the manual index.
Help and information about Octave is also available on the WWW
at https://www.octave.org and via the help@octave.org
mailing list.
octave:115> help feather
'feather' is a function from the file /usr/share/octave/7.3.0/m/plot/draw/feather.m
-- feather (U, V)
-- feather (Z)
-- feather (..., STYLE)
-- feather (HAX, ...)
-- H = feather (...)
Plot the '(U, V)' components of a vector field emanating from
equidistant points on the x-axis.
If a single complex argument Z is given, then 'U = real (Z)' and 'V
= imag (Z)'.
The style to use for the plot can be defined with a line style
STYLE of the same format as the 'plot' command.
If the first argument HAX is an axes handle, then plot into this
axes, rather than the current axes returned by 'gca'.
The optional return value H is a vector of graphics handles to the
line objects representing the drawn vectors.
phi = [0 : 15 : 360] * pi/180;
feather (sin (phi), cos (phi));
See also: plot, quiver, compass.
Additional help for built-in functions and operators is
available in the online version of the manual. Use the command
'doc <topic>' to search the manual index.
Help and information about Octave is also available on the WWW
at https://www.octave.org and via the help@octave.org
mailing list.
octave:116> figure
octave:117> imshow([1 0; 0 1])
octave:118> imshow(1:255)
octave:119> imshow([1 .5; .5 1])
octave:120> whos
Variables visible from the current scope:
variables in scope: top scope
Attr Name Size Bytes Class
octave:124> whos
octave:125> x = [1 0; 0 1]
x =
1 0
0 1
octave:126> whose
error: 'whose' undefined near line 1, column 1
octave:127> whos
Variables visible from the current scope:
variables in scope: top scope
Attr Name Size Bytes Class
==== ==== ==== ===== =====
x 2x2 32 double
Total is 4 elements using 32 bytes
octave:128> imshow(x)
octave:129> imshow(int(x))
error: 'int' undefined near line 1, column 8
octave:130> int
int16 int64 integral2 interp2 interpn intmin
int2str int8 integral3 interp3 intersect
int32 integral interp1 interpft intmax
octave:130> imshow(int8(x))
error: imshow: invalid data type for image
error: called from
imshow at line 199 column 9
octave:131> close all
octave:132> image = reshape(linspace(0, 1, 12), 2, 2, 3)
image =
ans(:,:,1) =
0 0.1818
0.0909 0.2727
ans(:,:,2) =
0.3636 0.5455
0.4545 0.6364
ans(:,:,3) =
0.7273 0.9091
0.8182 1.0000
octave:133> imshow(image)
octave:134> image(:, :, 3) = 0
image =
ans(:,:,1) =
0 0.1818
0.0909 0.2727
ans(:,:,2) =
0.3636 0.5455
0.4545 0.6364
ans(:,:,3) =
0 0
0 0
octave:135> imshow(image)
octave:136> image(:, :, 2) = 0
image =
ans(:,:,1) =
0 0.1818
0.0909 0.2727
ans(:,:,2) =
0 0
0 0
ans(:,:,3) =
0 0
0 0
octave:137> imshow(image)
octave:138> close all
octave:139>

152
lessons/lesson03/plotting.m Normal file
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%% Lesson 5a: Plotting
%
% We are going to go through several plotting schemes, and explore how you
% can customize plotting. We would go through 2D plotting, surface
% plotting, subplot, stem plot and 3D plotting
%
% In this file the `command syntax` style of functions will be used when
% possible, just to get you familiar with the style.
clear; clc; close all;
%% 2D plotting: line graphs
% In general, always annotate your plots appropriately! Use a title,
% axis labels, legends, etc. as necessary. Set appropriate bounds,
% appropriate scaling (e.g., linear vs. logarithmic), and the correct
% type of plot. We'll start simple with line plots.
x = -10:0.1:10;
y = x.^3;
y2 = x.^2;
hold on; % plotting more than 1 plot on 1 figure rather than overwriting
plot(x, y, 'DisplayName', 'x^3');
plot(x, y2, 'DisplayName', 'x^2');
hold off;
xlabel 'x axis';
ylabel 'y axis';
title 'Example 1';
xlim([-10 10]);
ylim([-10 10]);
% axis([-10 10 -10 10]);
grid on;
legend show; % 'DisplayName does this
%% Example 2: Plotting sine and cosine
t = 0:.1:10;
d1 = sin(t);
d2 = cos(t);
figure;
% plot(t, [d1.' d2.']);
% plot(t, d1, t, d2);
hold on;
plot(t, d1);
plot(t, d2);
hold off;
title 'Trig Functions';
% We can use some LaTeX-like symbols like \mu, \beta, \pi, \leq, \infty.
% For full LaTeX support use the `Interpreter: latex` option
xlabel 'time (\mu)s';
ylabel voltage;
legend sin cos;
% Save to file; gcf() is "get current figure"
exportgraphics(gcf(), "sample_plot.png");
%% More plotting options
% Legends, axis ticks (and labels), LaTeX interpreter
figure;
% Options for changing line pattern and color.
% Don't need `hold on`/`hold off` if multiple lines plotted with a single
% `plot` function.
plot(t, d1, 'b-.', t, d2, 'rp');
title 'Trig Functions';
xlabel 'time ($\mu$s)' Interpreter latex
ylabel voltage;
legend('sin', 'cos');
xticks(0:pi/2:10);
xticklabels({'0', '\pi/2', '\pi', '3\pi/2', '2\pi', '5\pi/2', '3\pi'});
% Many other options availible for plotting. Check the documentation or
% search online for options.
%% Subplots
% Subplots exist for stylistic purposes. Let's say you have a signal and
% you want to plot the magnitude and phase of the signal itself. It would
% make more sense if the magnitude and phase plots exist in the same
% figure. There are several examples fo subplot below to explain how it
% works. Note that linear indexing of plots is different from normal linear
% indexing.
figure;
subplot(2,2,1); % subplot(# of rows, # of columns, index)
plot(t,d1);
hold on;
plot(t, d2);
title 'Normal plot';
subplot(2, 2, 2); % index runs down rows, not columns!
plot(t, d1, 'b-.', t, d2, 'rp');
title 'Customized plot';
%% Stem plots
% stem plots are particularly useful when you are representing digital
% signals, hence it is good (and necessary) to learn them too!
% subplot(2,2,[3 4]) % takes up two slots
subplot(2, 1, 2);
hold on;
stem(t, d1);
stem(t, d2);
hold off;
title 'Stem plots';
sgtitle Subplots;
%% Tiling -- like subplots but newer
figure;
tiledlayout(2, 2);
nexttile;
plot(t, d1);
nexttile;
plot(t, d2);
%% A 3-D parametric function
% A helix curve
t = linspace(0,10*pi);
figure;
plot3(sin(t), cos(t), t);
xlabel sin(t);
ylabel cos(t);
zlabel t;
text(0, 0, 0, 'origin');
grid on;
title Helix;
%% Surface plot
% A shaded look for 2-D functions
%
% $f(x) = x\exp -(x^2+y^2)$
a1 = -2:0.25:2;
b1 = a1;
[A1, B1] = meshgrid(a1);
F = A1.*exp(-A1.^2-B1.^2);
figure;
surf(A1,B1,F);
%% Mesh plot
% A wireframe look for 2-D functions
figure;
mesh(A1,B1,F);