I found this very interesting cheat sheet about Octave here:
Source http://altons.github.io/octave/2013/05/05/octave-commands-cheat-sheet/
I think it is very great, but there are couple of commands missing (like PS1, which in my opinion makes your life better!).
So I have taken it and extendend with some commands.
Management & Help
Task
|
Command
|
exits software
|
quit or exit
|
list variables in session
|
who
|
list variables in session with info about type
|
whos
|
deallocate variable(s)
|
clear varname
|
displays search path
|
path
|
Adds path to search
|
addpath
|
clear screen
|
clc
|
list .m files in dir
|
what
|
search for keyword
|
lookfor
|
displays help for function
|
help funname
|
Parse and execute the contents of FILE
|
source(".octaverc")
|
List installed packages
|
pkg list
|
Install packages
|
pkg install [-auto or -noauto] pkg_name.tar.gz
|
Describe packages
|
pkg describe pkg_name
|
Load/Unload package
|
pkg load/unload pkg_name
|
Uninstall package
|
pkg uninstall pkg_name
|
Shell Commands
Task
|
Command
|
Change Linde starter
|
PS1(‘desired Starter’); %PS1(‘>> ‘);
|
change working directory to dir
|
cd dirname
|
print working directory
|
Pwd
|
print directory listing
|
ls
|
return value of named environment variable
|
getenv (string)
|
execute arbitrary shell command string
|
system (cmd)
|
Load the file
You will load a file and make it available with a
Varible having same name of the file without extension
|
Load FILENAME_IN_PWD
Load(‘FILENAME_IN_PWD’);
|
Save variable into file
You will load a file and make it available with a
Varible having same name of the file without extension
|
save FILENAME_IN_PWD
VARIABLE_NAME;
|
Special Operators
Definition
|
Operator
|
Example
|
comment
|
%
|
% Initialising
|
wildcard
|
*
|
clear p*
|
array
|
[ ]
|
[1 2; 3 4]
|
Cell Arrays
|
{ }
|
p = { 10 , 15 , "rectangle" }; p{1} =10
|
ranges
|
start:step:stop (default step=1)
|
1:10 or 1:10:100
|
variable assignment
|
=
|
A=magic(3);
|
do not display
|
;
|
a=1;
|
Workflow
Task
|
Command
|
Suspend the execution of the program.
|
pause; or pause(5)
|
print string to the stout
|
fprintf("Hello World")
|
Vectors & Matrices
Rules
· Square brackets delimit literal matrices.
· Commas separate elements on the same row.
· Semicolons separate rows.
· Commas may be replaced by spaces, and
· semicolons may be replaced by one or more newlines.
· Elements of a matrix may be arbitrary expressions, provided that all the dimensions agree.
· Optional: Matrices are denoted by uppercase letters A,B,X etc while vectors by lowercase letters a,b,y etc.
· Commas separate elements on the same row.
· Semicolons separate rows.
· Commas may be replaced by spaces, and
· semicolons may be replaced by one or more newlines.
· Elements of a matrix may be arbitrary expressions, provided that all the dimensions agree.
· Optional: Matrices are denoted by uppercase letters A,B,X etc while vectors by lowercase letters a,b,y etc.
Example
|
Expression
|
enter a row vector
|
[ x, y, ... ]
|
enter a column vector
|
[ x; y; ... ]
|
enter a 2×2 matrix
|
[ w, x; y, z ]
|
Return a row vector with N linearly spaced elements between BASE and
LIMIT
|
linspace (BASE, LIMIT, N)
|
Similar to linspace except that the values are logarithmically
spaced
|
logspace(BASE, LIMIT, N)
|
Higher Dimensional Arrays
|
B(z,y,z)=1
|
Sorting arrays
|
sort(A); or sort(A, 'descend');
|
Return true if any element in array is non-zero
|
any(A)
|
Return true if all element are non-zero
|
all(A)
|
Return a vector of indices of a matrix
|
[i , j] = find(A<0.5)
|
Array Operations
Task
|
Function
|
select elements of a vector
|
A(i)
|
select elements of a matrix
|
A(i,j)
|
select rows (columns) corresponding to the elements of a range
|
A(1:2,1); A(1:2,1:5);
|
select all rows (columns)
|
A(:,1); A(3,:);
|
Delete a row/column of a matrix
|
A(2,:)= [] or A(:,5) = []
|
Linear Algebra
Task
|
Function
|
dimensions of the array
|
size
|
returns larger dimension
|
length
|
allocates array with 0’s
|
zeros
|
allocates array with 1’s
|
ones
|
transpose array
|
'
|
Compute the determinant of A.
|
det(A)
|
inverse of matrix
|
inv
|
pseudo inverse of matrix
|
pinv
|
Calculate Eigenvalues / Eigenvectors of matrix A
|
eig(A) or [V,L] = eig(A)
|
Identity matrix
|
eye
|
Compute the rank of a Matrix
|
rank(A)
|
returns the lower triangular part of A
|
tril(A)
|
returns the upper triangular part of A
|
triu(A)
|
Create an N-by-N magic square
|
magic
|
Compute the dot product of two vectors
|
dot(A,B)
|
Compute the vector cross product of two 3-dimensional vectors X and Y
|
cross(X,Y)
|
interval range arrays
|
v = 1:0.1:2
%vector = STARTING_AT:DELTA:ENDING_AT
|
Plotting
|
Task
|
Command
|
Example
|
|
2-D plot
|
plot
|
plot(x,y); plot(x, a+b+c);
|
|
Surface plot
|
surf
|
surf(theta0, theta1, J);
|
|
Contour plot
|
contour
|
contour(theta0, theta1, J, logspace(-2, 3, 20))
|
|
Specify x-, y-, or z-axis labels for the current axis
|
[x,y,z]label
|
xlabel('k lags')
|
|
Set a plot window to plot window N
|
figure
|
figure;plot(x, a);
|
|
close figure window(s)
|
close
|
close [***(N),all,all hidden***]
|
|
new graphic objects are added to the plot
|
hold
|
hold on;plot(x, b);
|
|
Clear plot and restore default graphics settings
|
hold
|
hold off;
|
|
Display a legend for the axes
|
legend
|
plot(X,Y);legend('Temperature', 'Gas Demand');
|
|
give a title
|
title
|
title('myTitle');
|
|
export the chart
|
print
|
Print –dpng ‘filename.png’
|
Math Functions
Type
|
Function
|
Examples
|
Sum of elements along dimension DIM
|
sum
|
sum([1 2 3 4])
|
Product of elements along dimension DIM
|
prod
|
prod([1 2 3 4)]
|
Trigonometric
|
sin, cos, tan
|
floor((1+tan(1.2)) / 1.2)
|
Inverse Trigonometric
|
asin, acos, atan
|
|
Natural Logarithm
|
log
|
|
Base 10 Logarithm
|
log10
|
log10(100)/log10(10)
|
Exponentiation
|
exp
|
exp(0)
|
Absolute value
|
abs
|
abs(-3)
|
Square Root
|
sqrt
|
sqrt(3^2 + 4^2)
|
X raised to the Y power
|
power(X,Y)
|
power(3,2)
|
Real part of complex number
|
real
|
real(3+5I)
|
Imaginary part of complex number
|
imag
|
imag(3+5I)
|
Evaluate polynomials
|
polyval
|
polyval([2 10.1 0 6],0)
|
Write formatted polynomial
|
polyout
|
polyout([2 -3 1],"x")
|
Return the largest integer not greater than X
|
floor
|
floor(1.9)
|
Return the smallest integer not less than X
|
ceil
|
ceil(3.7)
|
Return the integer nearest to X
|
round
|
round(1.9)
|
Truncate fractional portion of X and return the integer portion
|
fix
|
fix(pi)
|
Stats Functions
Task
|
Example
|
Function
|
Uniform random numbers btw 0 and 1 (both excluded)
|
rand
|
rand(3,5)
|
Normal(0,1) random numbers
|
randn
|
randn(1,3)
|
Gamma distribution
|
randg
|
randg
|
Exponential distribution
|
rande
|
rande(1,10)
|
Poisson distribution
|
randp
|
randp(0.5,3,3)
|
Min value by column
|
min
|
min(A)
|
Max value by column
|
max
|
max(A)
|
Constants
Name
|
Expression
|
Default Variable
|
ans
|
Pi
|
pi
|
Euler's number
|
e
|
Imaginary number
|
i, j and I
|
Infinity
|
inf
|
Not a Number
|
NaN
|
machine precision
|
eps
|
true/false
|
logical 1/0
|
Logical Operators
Expression
|
Operator
|
is greater than
|
>
|
is less than
|
<
|
is greater than or equal to
|
>=
|
is less than or equal to
|
<=
|
is equal to
|
==
|
is not equal to
|
∼= or !=
|
AND with short circuiting
|
&&
|
with short circuiting
|
||
|
AND
|
&
|
OR
|
|
|
NOT
|
∼
|
Auxiliary Functions
Task
|
Function
|
Check a scalar
|
isscalar(a)
|
Check a vector
|
isvector(b)
|
Check a matrix
|
ismatrix(b)
|
is func available
|
is TAB TAB
|
Type info
|
typeinfo(b)
|
String Functions
Task
|
Function
|
Example
|
Compare 2 strings
|
strcmp
|
strcmp("hello","Hello")
|
Import & Export Data
Task
|
Command
|
Example
|
Read the matrix DATA from a text file
|
dlmread (FILE, SEP, R0, C0)
|
dmlread("virus.dat",",",1,1);
|
Write data to a text file
|
dlmwrite (FILE, M, DELIM, R, C)
|
dlmwrite("out.txt",yhat,";",1,1);
|
Read the csv files
|
csvread (FILENAME, DLM_OPTS)
|
csvread("input.csv");
|
Write csv files
|
csvwrite (FILENAME, X, DLM_OPTS)
|
csvwrite("output.csv", yhat);
|
Defining Functions
Simplest Form
function name
body
end
Example:
function wakeup
printf ("\a");
end
Passing Params
function name (arg-list)
body
end
Example:
function wakeup (message)
printf ("\a%s\n",
message);
end
wakeup ("Rise and shine!");
Return Single Value
function ret-var = name (arg-list)
body
end
Example:
function retval = avg (v)
retval = sum (v) / length (v);
end
Return Multiple Values
function [ret-var1,ret-var2,…,ret-varn] = name (arg-list)
body
end
Example:
function [mu,sigma] = basicStat(X)
mu = mean(X);
sigma = std(X);
end
Statements
IF Statement
if (condition)
then-body
elseif (condition)
elseif-body
else
else-body
end
Example:
if (rem (x, 2) == 0)
printf ("x is even\n");
elseif (rem (x, 3) == 0)
printf ("x is odd and divisible by 3\n");
else
printf ("x is odd\n");
end
Note that the elseif
keyword must not be spelled else if, as is allowed in Fortran. If
it is, the space between the else and if will tell
Octave to treat this as a new if statement within another if
statement's else clause
SWITCH Statement
switch (X)
case 1
do_something ();
case 2
do_something_else ();
otherwise
do_something_completely_different ();
end
Example:
A = 7;
switch A
case { 6, 7 }
printf ("variable is either 6 or 7\n");
otherwise
printf ("variable is neither 6 nor 7\n");
end
One advantage of using the switch statement compared to using
if statements is that the labels can be strings
switch (X)
case "a string"
do_something
...
endswitch
WHILE Statement
while (condition)
body
end
Example:
fib = ones (1, 10);
i = 3;
while (i <= 10)
fib (i) = fib (i-1) + fib (i-2);
i++;
end
DO-UNTIL Statement
do
body
until (condition)
Example:
fib = ones (1, 10);
i = 2;
do
i++;
fib (i) = fib (i-1) + fib (i-2);
until (i == 10)
FOR Statement
for var = expression
body
end
Example:
fib = ones (1, 10);
for i = 3:10
fib (i) = fib (i-1) + fib (i-2);
end
