# How to write the first line of a function?

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Mary292 on 13 Jan 2015
Commented: Image Analyst on 9 Mar 2015
I have a matrix of data, X. I need to create a function that will plot all columns of this data in a given number of different figures. The function should be called composite_plot. The function should have two inputs, the first will be the data, X, the second input will be the number of figures to be produced. For example, a call to composite_plot(X,10), should produce ten figures.
How would I write the first line of the function? I've never written a function before and so don't really know how many inputs and outputs to have or what to call them. I know it should be set out something like this
function[?]=composite_plot(?,?)
Can anyone help?
Image Analyst on 9 Mar 2015
I think questions about homework should be allowed, but the ideal way is to "Tag" them as homework so we know that we should just give hints rather than outright solutions . This is better than not tagging, getting a full solution, then editing away the question. Of course probably only like 10% of posters tag their own homework questions as homework. How do we let first-time posters know about the homework tag? Maybe they would tag it as homework if they knew that was the ethical/proper way to post.

Iain on 13 Jan 2015
Edited: Iain on 13 Jan 2015
The first line of a function should look something like this:
function [a b c] = something(a, b, c) % 3 inputs, 3 outputs
function something(a,b) % 2 inputs, 0 outputs
function varargout = something(varargin) %any number of inputs and outputs
function a = something(varargin) % 1 output, any number of inputs.
function [a b c d varargout] = something % no inputs, 4 outputs MINIMUM
function something(a,b,c,d,varargin) % no outputs, 4 inputs MINIMUM.
You should use sensible variable names, instead of random letters like I did. varargin and varargout are more advanced features that let you deal with variable numbers of inputs and outputs. nargin and nargout are what tells you how many inputs & outputs you have if you want to use them.
You should also remember that any input or output can be an array.