# Creating phase plot from initial data

8 vues (au cours des 30 derniers jours)
Gavin Seddon le 30 Mar 2017
Commenté : Star Strider le 21 Mar 2018
I have a data table with no associated function, is it possible to generate the vector field and phase diagram from this? GS.
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KSSV le 30 Mar 2017
What data you have?
Gavin Seddon le 15 Nov 2017
You are welcome, I have tried the arc tangent with my table and it appears I should define two points and calculate the angle. Also I cannot calculate the gradient since it complains that my matrix is not equal, Possibly because I am using fxy (multivariate). Nevertheless I have been of data now to complete the job. GS.

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### Réponse acceptée

Star Strider le 30 Mar 2017
Use the gradient function to create the derivatives.
See if this works with your data:
x = sin(0:0.5:2*pi*2); % Create Data
y = cos(0:0.5:2*pi*2); % Create Data
u = gradient(x); % Calculate ‘x’ Derivative
v = gradient(y); % Calculate ‘y’ Derivative
figure(1)
quiver(x, y, u, v)
grid
axis equal
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Gavin Seddon le 21 Mar 2018
Hello, I have decided the best way forward is to draw a labelled triangle. Then using my derivative as the absolute hypotenuse Value, then the angle cos = adjacent/hypotenuse. Thank you. GS.
Star Strider le 21 Mar 2018
My pleasure.

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