Step 6: Plot σ_x vs. r_i , Take 4: Functions

Let's create a function to calculate the bending stress that outputs σ_x given (M, r_i, r_o ).

Before we start doing this bring up the help file for creating functions in MATLAB. You can find it in the directory specified below:

Help > Contents > MATLAB > Programming > M-File Programming > M-File Scripts and Functions > M-File Functions.

Look at Simple Function Example: The average function that calculates the average of the elements in a vector. As you can see MATLAB has a very good help support system that you can use as a reference whenever you run into problems.

As you can see the correct syntax for creating a funcion is:

function return_value = function_name(parameter_1, parameter_2,...)

%function description - MUST  be in a comment

code...

return_value = value

Start by creating the bending stress function that outputs σ_x given (M, r_i, r_o ).

 
Save this as bending_stress.mMake a copy of beam3.musing Save As ... call the new file beam5.m

Comment out

Call function bending_stress
Run and check output

Before we part, let's remind ourselves of some important programming guidelines that we have followed in this tour:

• Develop code incrementally, testing obsessively at each stage. Develop a plan for how you are going to build your code before you sit at the computer.
• Dig through the MATLAB help diligently to figure out how to use specific functions etc. Usually, the examples are the best place to start. This is a better strategy than desperately hunting for the TA every time you need help with your code.
• Comment your program liberally.