Lectures, code examples, and practice questions for teaching MATLAB for applications in undergraduate chemical engineering classes.
Feel free to copy the code provided into your own MATLAB scripts to check your work! Please remember that although these are answers, there are multiple ways of doing the problem(s). We encourage you to develop your own method of writing and organizing your code!
%Creating Values
x_values = linspace(0,100,101);
y_values1 = 2.*(x_values).^2 + x_values.^3;
y_values2 = x_values.^(3-x_values);
Notes:
When creating the values, I used the command called linspace. What it does is that it creates a n x 1 matrix of evenly spaced values from an initial value to a final values. By default, it will create a list of 100 values unless specified. The way that it is called is the by the following:
MathWorks: linspace
linspace(lower_bound,upper_bound,number_of_values)
So in this case, I have created 101 values that are evenly spaced from 0 to 100. When you run this, you should see that it goes from 0 to 100 going up by 1. In this particular case, there is another method in which I could have called this:
x_values = lower_bound:step:upper_bound
However, linspace is much quicker when it comes to creating decimals. Such as if we attempt to create 36 values between 0 and 8. Try it yourself with both methods!
%Plotting on SAME graph
plot(y_values1,x_values);
hold on
plot(y_values2,x_values);
%Plot Labels
xlabel("Independent")
ylabel("Dependent")
title('MATLAB Plotting')
legend('Y Values 1','Y Values 2')
%Creating Limits for Axis
xlim([0,5])
ylim([0,5])
hold off
Notes:
Notice here when I wanted to graph another plot on the same graph, I had to call hold on. This makes it so that any further modifications I do are going to be placed on the same graph. When finished with the modifications, hold off is called so that when I attempt to make any further modifications, the previous graph is not modified.
Week 2: Plotting Multiple Lines
Another thing that should be noted is how the legend works. The first label is used for the first set of data points and the second label for the second data points and so on.
Week 2: General Plot Customizing
%Plotting on DIFFERENT graphs
%Graph 1
plot(y_values1,x_values);
hold on
%Plot Labels
xlabel("Independent")
ylabel("Dependent")
title('MATLAB Plotting')
legend('Y Values 1')
%Creating Limits for Axis
xlim([0,5])
ylim([0,5])
hold off
%Graph Problem 2
plot(y_values2,x_values);
hold on
%Plot Labels
xlabel("Independent")
ylabel("Dependent")
title('MATLAB Plotting')
legend('Y Values 2')
%Creating Limits for Axis
xlim([0,5])
ylim([0,5])
hold off
Notes:
Above is an example of the hold on and hold off idea mentioned before.
function ansW2fun(x_values)
y_values1 = 2.*(x_values).^2 + x_values.^3;
y_values2 = x_values.^(3-x_values);
%Plotting on SAME graph
plot(y_values1,x_values);
hold on
plot(y_values2,x_values);
%Plot Labels
xlabel("Independent")
ylabel("Dependent")
title('MATLAB Plotting')
legend('Y Values 1','Y Values 2')
%Creating Limits for Axis
xlim([0,5])
ylim([0,5])
hold off
end
Notes:
Once again, I’ve just copied the lines from the previous exercises and have the dependent values evaluated in the function as well. You can see here that the function does not return any values, however it will still display the graphs.