Reference

• Need help about a function?
• Operators
• Strings
• Built-in constants
• Use files
• Functions
• Commonly used commands
  • I/O
  • Matrix
  • Plots

Need help about a function?

help <function_name>

Operators

• ==.
• ~=: the same of !=.
• <, >, <=, >=.
• ~: logical not.
• &.
• |.
• xor.
• ': transpose a matrix.
• +, -, *, /.
• .<op>: where <op> could be +, -, * or /; it execute that operation element wise.

Strings

'it is a string'

Built-in constants

• pi.
• i, j: imaginary unit.
• Inf: infinite (1/0).
• NaN: not a number (0/0).
• eps: machine precision.
• realmax, realmin.

Use files

Inside the current working directory create a file with the .m extension. You can use that file as matlab script simply calling it into the terminal (you can omit the extension when calling):

<file_name>

Functions

function [output_params]=function_name(input_params): output_params and input_params are two comma separated variable lists.

Commonly used commands

I/O

• input('string'): it print 'string' and wait for keyboard input.
• fprintf('string and/or formats', output list): it print a sequence of chars, substituiting special symbols with output list content.
  E.g. of formats:
  • %g: fixed/floating point.
  • %e: exponential.
  • %s: string.
• open <file_name>: it opens a file.

Matrix

• eye(n): identical matrix n x n.
• zeros(m,n), ones(m,n): m x n matrix filled respectively with 0 and 1.
• size(x): it compute size of array x.
• length(v): it compute component number of vector v.
• diag(M): it produces a vector containing diagonal of M.
• diag(v): it produces a square matrix with v as diagonal and 0 otherwise.
• tril(M,i), triu(M,i): it extract from M all elements respectively below and above diagonal with index i (default i=0), including the diagonal itself.
• sum(M), prod(M): it compute respectively the sum and the product vector of elements of each M column.

Plots

• plot(x,y,'<options>'): it plots polyline which connects dots of two given linear spaces x and y. It is possible to provide some options.
• plot3(x,y,z,'<options>'): 3D plot.
• hold on: it keeps on the previously plotted graphic.
• hold off: it disable hold on.
• figure: opens a graphical window.
• subplot: it divides a graphical window in two or more graphical areas. subplot(n,m,p) divides the window in n x m graphical areas and next plot will modify p-th area.
• title('string'): assign a title to the graphic.
• xlabel('string'), ylabel('string'): assign a label to axis.
• legend('string1', 'string2', ...): creates a legend.
• axis([xmin,xmax,ymin,ymax]): fix extremes of graphic.
• semilogy, semilogx: sets axis in logarithmic scale.
• loglog: sets all axis in logarithmic scale.
• meshgrid(x,y): creates a 2D surface .
• mesh(x,y,z): creates a 3D surface with colored lines.
• surf(x,y,z): the same of mesh, but it colors also faces.
• view(angle, height): specifies the inizial point of view fo the graphic (default = -37.5, 30).
• colorbar: it shows the colorbar on the side.
• colormap('<name>'): it defines the color mapping (default = 'Jet').
• contour(x,y,z,v): displays level curves. v is optional, it gives the possibility to specify which levels to print.
• imread, imshow, imwrite: respectively reads image from a file, visualizes an image and saves an image.