# Plotting the apparent velocity

Here, betaA() is a user-specified function which returns the value of based on the value of and we put in. You need to write your own betaA function M-file before you can continue!

You can test your betaA function by using =0 and =90:

bA = betaA(0.99, 0)

bA =

0


bA = betaA(0.99, 90)

bA =

0.9900



Are these results what you expected?

Now, get prepared to plot the transverse velocity. First, let's create an array for using linspace:

theta = linspace(0, 180, 200);


Also create an array of values:

beta = [0.5, 0.7, 0.9, 0.995, 0.999, 0.9999];


and an array containing color options for plot:

clrs = ['r', 'y', 'g', 'b', 'k', 'm'];


Don't forget to set up a figure window:

figure(1); clf;
hold on;


Now let's make plot using for loop to save some typing. The for loop repeats a group of statements by a fixed, predetermined number of times, and a matching end delineates the statements:

for i = 1:6
bA = betaA(beta(i),theta);
plot(theta, bA, clrs(i))
end


And you can add graphic info AFTER the for loop:

title('Plot of Apparent Velocity')
xlabel('theta (angle to line of sight)')
ylabel('Apparent velocity (normalized to c)')
legend('0.5', '0.7', '0.9', '0.995', '0.999', '0.9999', 'Location', 'NorthEast');


You can set the limits of the vertical axis so you can see structure of the equations for small beta's:

ylim([0 20])