Vectors must be the same length.

Hi there.I want to draw the following formula, but I get the following error

error: Vectors must be the same length.

why?

y(t) is a 41765*4 matrix and A=y(:,3).

for example y(:,3) having values as follows:

8.26665517322484e-08 - 3.08466436225798e-07i

2.94822110031966e-08 - 1.28642078260667e-07i

4.87811541654193e-08 + 1.34459400745398e-08i

5.20060276867161e-08 - 1.37015907821914e-07i

7.13757345297127e-08 - 2.06148057224859e-07i

8.21435079828878e-08 - 1.73652495134914e-07i

...

And my code in Matlab

tspan = [0 2e-9];                   % time interval, up to 2 ns
y0 = [0+eps,0+eps,0+eps,0+eps];     
[t,y] = ode45(@rate_eq_program_1,tspan,y0);
size(t);
t=t*1e9;
y = abs(y);                                         % Change As Necessary To Get The Desired Resullt


delta_omega_laser=diff(atan(real(y(:,3))./imag(y(:,3))));

figure(1)
g = plot(t,delta_omega_laser );   % divided to normalize
xlabel('time [ns]','FontSize',14);  % size of x label
ylabel('Arbitrary units','FontSize',14);    % size of y label
set(gca,'FontSize',14);                 % size of tick marks on both axis
legend('\delta_omega', 'Location','SE')  % legend inside the plot

Thanks in advance for helping!!

[darova]

diff is just difference between values:

dy(1) = y(2) - y(1);
dy(2) = y(3) - y(2);
%...

If you have 5 elements in y arrays. How many would you have in dy?

[mohammad heydari]

I mean derivation and implementation of formulas, not differences.y are calculated in ode and i want to calculate formulas.

Answer 1

[M]

What lines causes the error ? Following one ?

g = plot(t,delta_omega_laser ); 

t and delta_omega_laser must have the same length.

[mohammad heydari]

But both have the same length. I say this from workspace.

both have 41765.

[darova]

• But both have the same length

impossible. Please show

[mohammad heydari]

this is workspace and please pay attention to t and y----------y is a matrix with 41765*4

[M]

Yes, t and y have same dimensions, but you are trying to plot not t and y but t and delta_omega_laser.

Using the diff command, you lose one element in your vector.

[mohammad heydari]

Of course, delta_omega_laser. is a function of y .

What advice do you have for writing that formula? Is there another way?

[darova]

You can shorten t vector

g = plot(t(2:end),delta_omega_laser); 

[mohammad heydari]

There was an error resolving your suggestion but there is a problem.I should have the red curve in the figure below.

But the shape I have is the following.The black and blue curves in the figure above are correctly obtained.

What is the problem?

[darova]

You forgot to divide by dt

dA=diff(atan(real(y(:,3))./imag(y(:,3))));
delta = -dA./diff(t);
tnew = t(2:end) - diff(t)/2;        % new vector "t" for delta
plot(tnew,delta)

Black points and curve is your original data y. Red points are positions where you calculate derivative

[mohammad heydari]

Thanks for your reply and I apologize for the delay in replying.

I got the following figure

This figure is much more promising than the previous one. But it's still not accurate.What other conditions do you recommend?

I just don't understand t (2: end) and tnew. What does this mean and why should it?

Best regards

[darova]

• I just don't understand t (2: end) and tnew. What does this mean and why should it?

Because the actual postion of a derivative between points:

So to draw correctly derivatives you have to correct you original t vector

How your graph looks like if you zoom in?

[mohammad heydari]

How your graph looks like if you zoom in?

As I put it above.Zooming in does not make a difference.

[darova]

Impossible. Can you attach the data?

[darova]

Try:

ylim([-1 1]*2e-7)

I don't know why you don't get the graph you want. I think the problem is deeper than it seems

Results make more sense if plot like this:

plot(real(y(:,3)),imag(y(:,3)),'.-b')

[mohammad heydari]

thanks alot for your help.

Trying to check again.