substituting multiple values in symbolic formula?
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Sharif Khalil
il 29 Giu 2018
Modificato: Walter Roberson
il 30 Giu 2018
I have this symbolic formula that is a variable of theta and phi, and I want to substitute the theta and phi with the following values in the following formula:
if true
% code
end
theta = -pi/2:pi/180:pi/2;
phi = -pi:pi/180:pi;
U = abs(sin(pi*cos(phi)*sin(theta))*sin(pi*sin(phi)*sin(theta)))^2/(abs(sin((pi*cos(phi)*sin(theta))/2))^2*abs(sin((pi*sin(phi)*sin(theta))/2))^2);
2 Commenti
Ameer Hamza
il 30 Giu 2018
theta and phi have different lengths. For substitution, they must have equal lengths.
Risposta accettata
Walter Roberson
il 30 Giu 2018
First create the symbolic formula. Next create your vectors of values but give them a different name than the variables in the formula. Then use ndgrid to create a grid of values for the two variables and use different variable names still. Finally,
Output = subs(U, {theta, phi}, {thetaGrid, phiGrid}) ;
There is another possibility that does not require creating the grid but it involves two subs calls and being careful about row and column vectors.
5 Commenti
Walter Roberson
il 30 Giu 2018
Modificato: Walter Roberson
il 30 Giu 2018
1) First create the symbolic formula.
syms theta phi real
Psi_x = k*dx*sin(theta)*cos(phi) + Beta_x;
Psi_y = k*dy*sin(theta)*sin(phi) + Beta_y;
AF_Field = (sin(Nx*Psi_x/2)/(sin(Psi_x/2)))*...
(sin(Ny*Psi_y/2)/(sin(Psi_y/2)));
U = abs((fi*AF_Field)).^2;
2) Next create your vectors of values but give them a different name than the variables in the formula.
Theta = -pi/2:pi/180:pi/2; % Elevation Angle (radian)
Phi = -pi:pi/180:pi; % Azimuth Angle (radian)
3) Then use ndgrid to create a grid of values for the two variables and use different variable names still.
[thetaGrid, phiGrid] = ndgrid(Theta, Phi);
4) Finally,
Output = subs(U, {theta, phi}, {thetaGrid, phiGrid}) ;
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