Plotting 2 lines in the same graph

How can i get the 2 plots to come out on the same figure?

%% Problem parameters

% Projectile

m = 0.05; % Mass of projectile (kg)

r = 0.03; % Radius of projectile (m)

theta = 25; % Initial angle (degrees)

y0 = 50; % Initial hieght (m)

x0 = 0; % Initial distance (m)

vu = 50; % Initial velocity (m/s)

vu_NOdrag = 50; % Initial velocty with no drag (m/s)

g = -9.81; % Gravity force (m/s^2)

% Drag

p = 1.183; % Density of air (kg/m^3)

Cd = 0.08; % Drag coefficeint

A = pi*r^2; % Area

% Initial conditions

x = x0;

y = y0;

x_NOdrag = x0;

y_NOdrag = y0;

ax = 0;

ay = 0;

ax_NOdrag = 0;

ay_NOdrag = 0;

sig = ((theta)*pi)/180; % converting degrees to radians

t = 0

t_NOdrag = 0

% Instantanious angle (changes with time)

RADangle = sig;

RADangle_NOdrag = sig;

% Arrays to store x and y values for each step

xCoordinates = [];

yCoordinates = [];

xCoordinates_NOdrag = [];

yCoordinates_NOdrag = [];

% Weight force (ball)

fg = -9.81 * m;

% Time step, the smaller the time step the more accurate the approximation.

% (closer to the analytical solution)

dt = 1;

dt_NOdrag = 1;

while y >= 0

fd = -0.5 * Cd * A * (vu^2); % DRAG SOLUTION

% Equations of motion

% Drag

fx = fd * cos(RADangle);

fy = fd * sin(RADangle) + fg;

% Acceleration components

% Drag

ax = fx/m;

ay = fy/m;

% Calculating velocity components using acceleration components

% Drag

vx = (vu*cos(RADangle) + (ax * dt));

vy = (vu*sin(RADangle) + (ay * dt));

% Define magnitude of velocity using velocity components

% Drag

vu = sqrt((vx^2) + (vy^2));

% Define angle using velocity components

% Drag

RADangle = atan2(vy,vx);

% Calculating possition using velocity and acceleration componets,

% and sort componets to respective lists

x = x + vx * dt + .5*ax*(dt^2);

xCoordinates = [xCoordinates x];

y = y + vy * dt + .5*ay*(dt^2);

yCoordinates = [yCoordinates y];

% Time increasing by incriments of the chosen time step

t = t + dt;

end

while y_NOdrag>=0

fd_NOdrag = 0; % NO DRAG SOLUTION

% No drag

fx_NOdrag = fd_NOdrag * cos(RADangle);

fy_NOdrag = fd_NOdrag * sin(RADangle) + fg;

% No drag

ax_NOdrag = fx_NOdrag/m;

ay_NOdrag = fy_NOdrag/m;

% No drag

vx_NOdrag = (vu_NOdrag*cos(RADangle_NOdrag) + (ax_NOdrag * dt_NOdrag));

vy_NOdrag = (vu_NOdrag*sin(RADangle_NOdrag) + (ay_NOdrag * dt_NOdrag));

% No drag

vu_NOdrag = sqrt(((vx_NOdrag)^2) + ((vy_NOdrag)^2));

% No drag

RADangle_NOdrag = atan2(vy_NOdrag,vx_NOdrag);

x_NOdrag = x_NOdrag + vx_NOdrag * dt_NOdrag + .5*ax_NOdrag*(dt_NOdrag^2);

xCoordinates_NOdrag = [xCoordinates_NOdrag x];

y_NOdrag = y_NOdrag + vy_NOdrag * dt_NOdrag + .5*ay_NOdrag*(dt_NOdrag^2);

yCoordinates_NOdrag = [yCoordinates_NOdrag y];

t_NOdrag = t_NOdrag + dt_NOdrag;

end

% Displaying results

disp(['Time taken to reach ground = ', num2str(t), ' seconds'])

disp(['Total distance travelled = ', num2str(x), 'metres'])

disp(['Time taken to reach ground (with NO drag) = ', num2str(t), ' seconds'])

disp(['Total distance travelled (with NO drag) = ', num2str(x_NOdrag), 'metres'])

plot(xCoordinates, yCoordinates);

xlabel('Distance (m)')

ylabel('Height (m)')

title('Ball Flight Path')

hold on

plot(xCoordinates_NOdrag, yCoordinates_NOdrag)

hold off

Answer 1

[Shubhankar Poundrik]

Hi Kyle,

I understand that you are trying to plot two plots in the same figure using the lines

plot(xCoordinates, yCoordinates); 
xlabel('Distance (m)')
ylabel('Height (m)')
title('Ball Flight Path')
hold on
plot(xCoordinates_NOdrag, yCoordinates_NOdrag)
hold off

However, only one plot seems to be visible when the code is run.

The code for plotting the data is correct. However, all values contained in the arrays xCoordinates_NOdrag and yCoordinates_NOdrag are all equal.

Following are their values.

xCoordinates_NOdrag =

160.4920 160.4920 160.4920 160.4920 160.4920

yCoordinates_NOdrag =

-27.6045 -27.6045 -27.6045 -27.6045 -27.6045

Thus, plotting them creates a single point on the figure. It can be better seen by adding a circular marker to the plot.

Replace the above code with the following.

plot(xCoordinates, yCoordinates); 
xlabel('Distance (m)')
ylabel('Height (m)')
title('Ball Flight Path')
hold on
plot(xCoordinates_NOdrag, yCoordinates_NOdrag, 'ro')
hold off

The problem seems to be with the values of the variables being plotted and not the code for plotting them.

Regards,

Shubhankar.

[Kyle Hamanne]

thankyou!

Answer 2

[Edgar Guevara]

Modify the last lines of your code:

disp(['Time taken to reach ground (with NO drag) = ', num2str(t), ' seconds'])
disp(['Total distance travelled (with NO drag) = ', num2str(x_NOdrag), 'metres'])


hold on 
plot(xCoordinates, yCoordinates, 'ro-'); 
xlabel('Distance (m)')
ylabel('Height (m)')
title('Ball Flight Path')
plot(xCoordinates_NOdrag, yCoordinates_NOdrag, 'kx-')
legend({'Drag' 'No Drag'})
hold off

[Kyle Hamanne]

[Kyle Hamanne]

I tried altering those final sections, still only plotted 1 line?