What is your favourite MATLAB/Octave programming trick? [closed]

Answer 1

Using the built-in profiler to see where the hot parts of my code are:

profile on
% some lines of code
profile off
profile viewer

or just using the built in tic and toc to get quick timings:

tic;
% some lines of code
toc;

Answer 2

Know your axis properties! There are all sorts of things you can set to tweak the default plotting properties to do what you want:

set(gca,'fontsize',8,'linestyleorder','-','linewidth',0.3,'xtick',1:2:9);

(as an example, sets the fontsize to 8pt, linestyles of all new lines to all be solid and their width 0.3pt, and the xtick points to be [1 3 5 7 9])

Line and figure properties are also useful, but I find myself using axis properties the most.

Answer 3

x=repmat([1:10],3,1); % say, x is an example array of data

l=x>=3; % l is a logical vector (1s/0s) to highlight those elements in the array that would meet a certain condition.

N=sum(sum(l));% N is the number of elements that meet that given condition.

cheers -- happy scripting!

Answer 4

Invoking Java code from Matlab

Answer 5

Turn a matrix into a vector using a single colon.

x = rand(4,4);
x(:)

Answer 6

Anonymous functions, for a few reasons:

1. to make a quick function for one-off uses, like 3x^2+2x+7. (see listing below) This is useful for functions like quad and fminbnd that take functions as arguments. It's also convenient in scripts (.m files that don't start with a function header) since unlike true functions you can't include subfunctions.
2. for closures -- although anonymous functions are a little limiting as there doesn't seem to be a way to have assignment within them to mutate state.

.

% quick functions
f = @(x) 3*x.^2 + 2*x + 7;
t = (0:0.001:1);
plot(t,f(t),t,f(2*t),t,f(3*t));

% closures (linfunc below is a function that returns a function,
% and the outer functions arguments are held for the lifetime
% of the returned function.
linfunc = @(m,b) @(x) m*x+b;
C2F = linfunc(9/5, 32);
F2C = linfunc(5/9, -32*5/9);