Help creating Z from X and Y for a contour plot

So I have values for X and Y in vector form (13 x 1) I need to generate matrix Z using those values to get a 13 x 13 matrix for my contour plot. So I want matlab to go calculate Z for every value of Y given a single value of X and so on.

figure(3)
force_amplitude=[1:13]'
force_time=[0:0.05:0.6]'

energy_consumption=20.093*12.5*((1.27/(force_amplitude*force_time))+force_time);
C=(1.27./(force_amplitude.*force_time))-force_time;

contour(force_amplitude,force_time,energy_consumption)

Answer 1

[Star Strider]

You need the invaluable assistance of the meshgrid function to make your dreams reality:

figure(3)
force_amplitude=1:13;
force_time=0:0.05:0.6;

[F_A, F_T] = meshgrid(force_amplitude, force_time);

energy_consumption = @(force_amplitude, force_time) 20.093*12.5*((1.27./(force_amplitude.*force_time))+force_time);
C = @(force_amplitude, force_time) (1.27./(force_amplitude.*force_time))-force_time;

contour(force_amplitude,force_time,energy_consumption(F_A, F_T))
xlabel('Force Amplitude')
ylabel('Force Time')

I created ‘energy_consumption’ (and ‘C’) as anonymous functions for convenience, then after vectorising them, called them from within your contour call. You can certainly create separate ‘Z’ matrices, for example:

Z = energy_consumption(F_A, F_T);

and then plot it.

If you are not already familiar with them, see the documentation on Anonymous Functions (link) for a full discussion.

In your code, you do not need the square brackets around the vectors, although if they make your code more readable for you, use them.

[Kevin Edlebeck]

I think i just did that the hard way.

figure(3)

force_amplitude=[1:13];
force_time=[0:0.05:0.6];

for i=1:13;
E(i,:)=20.093*12.5*((1.27./(force_amplitude(:,i).*force_time))+force_time);
end

for i=1:13;
C(i,:)=((1.27./(force_amplitude(:,i).*force_time))-force_time);
end

E=transpose(E)
contour(force_amplitude,force_time,C,-0.4:0.2:1.2,'ShowText', 'on')
hold on
contour(force_amplitude,force_time,E,180:20:440,'ShowText', 'on')
hold off

Is this the long way of doing what meshgrid does?

[Star Strider]

In a word: Yes!

MATLAB has the ability to vectorise calculations, so taking advantage of that ability will save you much frustration, code complexity, and computational time.

See the documentation on Vectorization for an extended discussion.