Octave
Table of Contents

Useful links
Problems with mac
displaying blank axis with aqua terminal
solution: change the terminal's type to x11
setenv GNUTERM x11
Plotting
plot a simple function
t=[0:0.01:2.00]
y=cos(2*pi*t)
legend('cos')
xlabel('time)
title('Cosine plot')
axis([5 5 1 1 ]); %the first two elements are x bound and the second tow are y bounds
plot (t,y)
plot 2 functions in one window
t=[0:0.01:2.00]
y1=cos(2*pi*t)
y2=t.**(1/2)
plot (t,y1)
hold on;
plot (t,y2)
plot in different windows
=[0:0.01:2.00]
y1=cos(2*pi*t)
y2=t.**(1/2)
figure(1); plot(t,y1);
figure(2); plot(t,y2);
plot 2 functions in one window side by side
t=[0:0.01:2.00]
y1=cos(2*pi*t)
y2=t.**(1/2)
subplot(1,2,1); %divides plot a 1X2 grids, access the first element
plot (t,y1);
subplot(1,2,2); %access the first element
plot (t,y2)
Saving plot in a directory
cd 'home/my_folder' ;
print dpng 'my_plot.png'
Clear figure
clf;
visualizing amtrix
A = magic(5)
imagesc(A)% draw a 5*5 grids of colors and colors are related to the values of matrix.
imagesc(A) , colorbar % add bar to the image
scripting in Octave
adding a folder to path
addpath('/scr/myscripts')
control statement
for
for i=1:10;
v(i) = 2^i ;
end;
while & if
i=1;
while i<=5,
v(i)=20;
i=i+1;
end;
%%%%% OR
i=1;
while true,
v(i)=20;
i=i+1;
if i==6,
break;
end;
end;
%%%%%%
if v(1)==20,
disp('The first one is equal to twenty');
elseif v(2)==5,
disp('The second one is equal to five');
else,
disp('Neither v(1) ==20 or v(2)==5')
defining function
like matlab, write function into a ".m" file.
function [y1 , y2]= squareandcube(x)
y1=x^2;
y2=x^3;
to call the function just cd to that directory and call that function no file calling in needed!!!
[v, w] =squareandcube(5);
matrix and linear algebra
defining matrix
A = [1 2 ; 4 5; 5 8]; %3*2 matrix
B= [4 2 7; 6 9 1] ; % 2*3 matrix
transpose, inverse etc
C=B*A; %matrix multiplication
A' %transpose
inv(C) %inverse
page revision: 25, last edited: 19 May 2013 21:48