## Contents

# plot02.m - Plotting y = sin(x)

x = linspace(0,2*pi,100); % define 100 x values from 0 to 2 pi y = sin(x); % calculate sin(x) plot(x,y) % plot y vs. x % set the plot limits on the x and y axes xlim([0, 2*pi]); ylim([-1.2, 1.2]); % label x and y axes and give the plot a title xlabel('\theta') ylabel('Sin(\theta)') title('Sine function over one period', 'FontSize',14)

This example plots `sin(x)` vs. `x`. The `linspace(0,2*pi,100)` command is used to create an array of 100 points evenly distributed from 0 to 2*pi.

The commands `xlim()` and `ylim()` are used to specify the limits of the x (horizontal) and y (vertical) axes. Each of these functions expects a 1x2 or a 2x1 vector that contains the lower and upper limits respectively. For example in the code above the x limits are specified as

xlim([0, 2*pi]);

The comma is not necessary, so the following command also works:

xlim([0 2*pi]);

However, the comma is recommended for beginning programmers as it produces more robust code. For example if you accidently put in an extra space around the asterisk the command `xlim([0, 2 *pi]);` would be fine, however the command `xlim([0 2 *pi]);` would give an error because `[0 2 *pi]` would be interepreted as a 1x3 matrix and the element `*3` does not make sense.

For those of you that like compact code, you can also replace the `xlim()` and `ylim()` commands with a single `axis` command. The `axis` command expects a 1x4 or a 4x1 array containing the min and max x values followed by the min and max y values. So, in this example, you could replace `xlim()` and `ylim()` commands with

axis([0, 2*pi, -1.2, 1.2]);

or

axis([0 2*pi -1.2 1.2]);

if you prefer elegance and don't mind slighly more error-prone syntax.

# Leaving off the xlim and ylim commands

Try commenting out the `xlim` and `ylim` statements and see what happens. Your plot should look like the following

Notice that the plot is now a bit asymmetrical. The plot axis starts at 0 and goes 7 rather than 2*pi. By default, Matlab extends the axis to the next whole number past the last data point. Also, it plots from -1 to +1 on the vertical axis causing the function to bump its head on the top of the plot. Using the `xlim` and `ylim` commands can help make your figures look more professional.