Matlab, quick review

[gusl]

* sweet syntactic sugar for matrix operations (transpose, submatrix, etc.)
* very easy to write unreadable code, full of poorly-named variables
* the semantics seems to be unnecessarily complex
* argh, please please let me define nameless functions, on the fly!

I know how to do entry-wise application (i.e. "mapcar" for the Lispers) when it's an infix operator: e.g. use ".*" instead of "*". But I can't do this for my own functions, and need to write for-loops.

A very odd thing: apparently, functions can't refer to constants/variables defined outside of it (the only constants allowed seem to be literals such as "1" and pre-defined constants, such as "pi").

Hopefully, I'm missing something.

Comments

[bhudson.livejournal.com]

If you are writing for loops, you're doing something wrong, and matlab will hurt you for it. Unfortunately, I haven't hacked matlab in a very long time so I can't actually help you.

Mapcar

[marymcglo.livejournal.com]

Is this what you're looking for?

arrayfun(@your_function_name, your_array)

See also cellfun. Matlab doesn't handle for loops well, so if you can avoid them you'll save a lot of time.

Re: Mapcar

[gustavolacerda.livejournal.com]

'@' (i.e. lambda) and 'arrayfun' were exactly what I needed! Thanks.

Nameless function

[(Anonymous)]

define nameless functions, on the fly:
anonymous functions
f = @(x) x^2+2x

- scott

Re: Nameless function

[stepleton.livejournal.com]

Yeah, that's how it's done in MATLAB (Now With Closures!). Hope you can do it all in one line. And Benoit is right: loops when you're learning usually == fail.

And I see you've already noticed MATLAB's delightful scoping. Don't use "evalin", okay? Just pass what you need. Stick it all in a struct if you have to.

Don't forget that you can create a new variable inside a block and refer to it outside of the block later, i.e.

function foo=myfunc

if true
a = 10;
end

foo = a^2;

Re: Nameless function

[gustavolacerda.livejournal.com]

Awesome! so @ is like lambda?

Scott who?

Re: Nameless function

[gustavolacerda.livejournal.com]

'@' and 'arrayfun' were exactly what I needed! Thanks.

[altamira16.livejournal.com]

feval is also useful to know. Carry on.