cs143 introduction to matlab (code).mht

it is a very essential matlab code.

there is no risk of</SPAN>
<SPAN class=3Dcomment>% conflicts with the variables in the main =
workspace. At the end of a</SPAN>
<SPAN class=3Dcomment>% function execution only the output arguments =
will be visible in the</SPAN>
<SPAN class=3Dcomment>% main workspace.</SPAN>
=20
a =3D [1 2 3 4];               <SPAN class=3Dcomment>% Global variable =
a</SPAN>
b =3D myfunction(2 * a)        <SPAN class=3Dcomment>% Call myfunction =
which has local </SPAN>
                             <SPAN class=3Dcomment>%   variable a</SPAN>
a                            <SPAN class=3Dcomment>% Global variable a =
is unchanged</SPAN>

[c, d] =3D <SPAN class=3Dcont>...</SPAN>
  myotherfunction(a, b)      <SPAN class=3Dcomment>% Call =
myotherfunction with two return</SPAN>
                             <SPAN class=3Dcomment>% values</SPAN>


<SPAN =
class=3Dcomment>%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%=
%%%%%%%%%%%%%%</SPAN>
<SPAN class=3Dcomment>%(7) Plotting </SPAN>

x =3D [0 1 2 3 4];             <SPAN class=3Dcomment>% Basic =
plotting</SPAN>
plot(x);                     <SPAN class=3Dcomment>% Plot x versus its =
index values</SPAN>
pause                        <SPAN class=3Dcomment>% Wait for key =
press</SPAN>
plot(x, 2*x);                <SPAN class=3Dcomment>% Plot 2*x versus =
x</SPAN>
axis([0 8 0 8]);             <SPAN class=3Dcomment>% Adjust visible =
rectangle</SPAN>

figure;                      <SPAN class=3Dcomment>% Open new =
figure</SPAN>
x =3D pi*[-24:24]/24;
plot(x, sin(x));
xlabel(<SPAN class=3Dstring>'radians'</SPAN>);           <SPAN =
class=3Dcomment>% Assign label for x-axis</SPAN>
ylabel(<SPAN class=3Dstring>'sin value'</SPAN>);         <SPAN =
class=3Dcomment>% Assign label for y-axis</SPAN>
title(<SPAN class=3Dstring>'dummy'</SPAN>);              <SPAN =
class=3Dcomment>% Assign plot title</SPAN>

figure;                     =20
subplot(1, 2, 1);            <SPAN class=3Dcomment>% Multiple functions =
in separate graphs</SPAN>
plot(x, sin(x));             <SPAN class=3Dcomment>%   (see "help =
subplot")</SPAN>
axis square;                 <SPAN class=3Dcomment>% Make visible area =
square</SPAN>
subplot(1, 2, 2);
plot(x, 2*cos(x));
axis square;

figure;                     =20
plot(x, sin(x));
hold on;                     <SPAN class=3Dcomment>% Multiple functions =
in single graph           </SPAN>
plot(x, 2*cos(x), <SPAN class=3Dstring>'--'</SPAN>);     <SPAN =
class=3Dcomment>% '--' chooses different line pattern</SPAN>
legend(<SPAN class=3Dstring>'sin'</SPAN>, <SPAN =
class=3Dstring>'cos'</SPAN>);        <SPAN class=3Dcomment>% Assigns =
names to each plot</SPAN>
hold off;                    <SPAN class=3Dcomment>% Stop putting =
multiple figures in current</SPAN>
                             <SPAN class=3Dcomment>%   graph</SPAN>

figure;                      <SPAN class=3Dcomment>% Matrices vs. =
images</SPAN>
m =3D rand(64,64);
imagesc(m)                   <SPAN class=3Dcomment>% Plot matrix as =
image</SPAN>
colormap gray;               <SPAN class=3Dcomment>% Choose gray level =
colormap</SPAN>
axis image;                  <SPAN class=3Dcomment>% Show pixel =
coordinates as axes</SPAN>
axis off;                    <SPAN class=3Dcomment>% Remove axes</SPAN>



<SPAN =
class=3Dcomment>%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%=
%%%%%%%%%%%%%%</SPAN>
<SPAN class=3Dcomment>%(8) Working with (gray level) images</SPAN>

I =3D imread(<SPAN class=3Dstring>'cit.png'</SPAN>);         <SPAN =
class=3Dcomment>% Read a PNG image</SPAN>

figure
imagesc(I)                    <SPAN class=3Dcomment>% Display it as gray =
level image</SPAN>
colormap gray;

colorbar                      <SPAN class=3Dcomment>% Turn on color bar =
on the side</SPAN>
pixval                        <SPAN class=3Dcomment>% Display pixel =
values interactively</SPAN>
truesize                      <SPAN class=3Dcomment>% Display at =
resolution of one screen</SPAN>
                              <SPAN class=3Dcomment>%   pixel per image =
pixel</SPAN>
truesize(2*size(I))           <SPAN class=3Dcomment>% Display at =
resolution of two screen</SPAN>
                              <SPAN class=3Dcomment>%   pixels per image =
pixel</SPAN>

I2 =3D imresize(I, 0.5, <SPAN class=3Dstring>'bil'</SPAN>); <SPAN =
class=3Dcomment>% Resize to 50% using bilinear </SPAN>
                              <SPAN class=3Dcomment>%   =
interpolation</SPAN>
I3 =3D imrotate(I2, 45, <SPAN class=3Dcont>...</SPAN><SPAN =
class=3Dcomment>     % Rotate 45 degrees and crop to</SPAN>
              <SPAN class=3Dstring>'bil'</SPAN>, <SPAN =
class=3Dstring>'crop'</SPAN>); <SPAN class=3Dcomment>%   original =
size</SPAN>

I3 =3D double(I2);              <SPAN class=3Dcomment>% Convert from =
uint8 to double, to allow</SPAN>
                              <SPAN class=3Dcomment>%   math =
operations</SPAN>
imagesc(I3.^2)                <SPAN class=3Dcomment>% Display squared =
image (pixel-wise)</SPAN>
imagesc(log(I3))              <SPAN class=3Dcomment>% Display log of =
image (pixel-wise)</SPAN>
I3 =3D uint8(I3);               <SPAN class=3Dcomment>% Convert back to =
uint8 for writing</SPAN>
imwrite(I3, <SPAN class=3Dstring>'test.png'</SPAN>)       <SPAN =
class=3Dcomment>% Save image as PNG</SPAN>

figure;
g =3D [1 2 1]' * [1 2 1] / 16;  <SPAN class=3Dcomment>% 3x3 Gaussian =
filter mask</SPAN>
I2 =3D double(I);               <SPAN class=3Dcomment>% Convert image to =
floating point</SPAN>
I3 =3D conv2(I2, g);            <SPAN class=3Dcomment>% Convolve image =
with filter mask</SPAN>
I3 =3D conv2(I2, g, <SPAN class=3Dstring>'same'</SPAN>);    <SPAN =
class=3Dcomment>% Convolve image, but keep original size</SPAN>
subplot(1, 2, 1)              <SPAN class=3Dcomment>% Display original =
and filtered image</SPAN>
imagesc(I);                   <SPAN class=3Dcomment>%   =
side-by-side</SPAN>
axis square;
colormap gray;
subplot(1, 2, 2)
imagesc(I3);
axis square;
colormap gray;

<SPAN =
class=3Dcomment>%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%=
%%%%%%%%%%%%%%</SPAN>
</PRE>
<H2>myfunction.m</H2><A id=3Dmyfunction name=3Dmyfunction></A><PRE =
class=3Dmcode><SPAN class=3Dkeyword>function</SPAN> y =3D myfunction(x)
<SPAN class=3Dcomment>% Function of one argument with one return =
value</SPAN>

a =3D [-2 -1 0 1];              <SPAN class=3Dcomment>% Have a global =
variable of the same name</SPAN>
y =3D a + x;
</PRE>
<H2>myotherfunction.m</H2><A id=3Dmyotherfunction =
name=3Dmyotherfunction></A><PRE class=3Dmcode><SPAN =
class=3Dkeyword>function</SPAN> [y, z] =3D myotherfunction(a, b)
<SPAN class=3Dcomment>% Function of two arguments with two return =
values</SPAN>

y =3D a + b;
z =3D a - b;
</PRE>
<HR>

<DIV class=3Dnavfoot>
<DIV class=3Dfootname>Created by <A=20
href=3D"mailto:%20roth%20(AT)%20cs%20DOT%20brown%20DOT%20edu">Stefan =
Roth</A>=20
</DIV>
<DIV class=3Dfootdate>Last updated: 2003-09-10 =
</DIV></DIV></BODY></HTML>

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