MATLAB: User defined functions

As you read this material we strongly recommend that you activate your MATLAB window and try the commands explained right there and then

MATLAB provides a convenient mechanism for using functions.

As we learned in C++, functions may receive data via their arguments and return values to the calling program via their names and/or their “passed by name” arguments. In C++, for simplicity, we always wrote our user defined functions in the same file as our main function. It is possible to write the C++ functions in their own files and then link the files together properly.

In MATLAB , again for simplicity, we will write each user defined function in a separate .m file and consider them as scripts ( just like the rest of .m files), except that they are going to be special scripts capable of receiving data and returning data.

Here is what the HELP facility of MATLAB has to say about function structure:

The name of the .m file must be the same as the name of the function as indicated below by the Help facility of MATLAB

We create a .m file which contains the above function and save it on a folder on our desktop.

Here is the file named stat.m

We can now use this function by simply invoking its name. The use of it is illustrated in the following picture of a script called , example.m where we define an array of scores and then use the function to calculate the statistics of the scores:

The following picture of the command window illustrates the results obtained when we type the name of the file example at the MATLAB command line. It also illustrates that when we type help stat we get the comments we included in our function from the second line until the end of the uninterrupted sequence of comment lines.