Error: Data must be numeric, datetime, duration, categorical, or an array convertible to double.

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Ammar 2024-7-7

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评论： Voss 2024-7-8

采纳的回答： Voss

Plotting_Theta_Phi_Function.m

Hello everyone,

I am trying to plot a function that has two different variables: theta and phi.

Theta = -pi/2:0.1:pi/2

Phi = Specific Values at 0 and pi/2

I have an error that says:

"Error: Data must be numeric, datetime, duration, categorical, or an array convertible to double."

I've tried looking up this error on different discussions. However, I wasn't able to find anything that helped with my specific scenario.

I have tried different methods and approaches: Using "symbolic variables", fimplicit function, fplot function, etc. However, I got different errors everytime I tried a different approach.

I attached my code for reference:

Plotting_Theta_Phi_Function.m

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Answer 1

Voss 2024-7-7

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https://ww2.mathworks.cn/matlabcentral/answers/2135276-error-data-must-be-numeric-datetime-duration-categorical-or-an-array-convertible-to-double#answer_1482381

在 MATLAB Online 中打开

Plotting_Theta_Phi_Function.m

tic

close all; clc;

% Declaring Theta and Phi Variables

theta = 0:0.1:pi/2;

% Phi Values

phi_E_Plane = 0;

phi_H_Plane = pi/2;

phi = [phi_E_Plane, phi_H_Plane];

% Declaring x and y variables as theta and phi

x = sin(phi);

y = cos(theta);

% Function Z is a combination of x and y

Z = @(x,y) x.^2.*y + y.^2.*x;

% Calculating E-Plane and H-Plane "values"

E_Plane = Z(theta,phi(1));

H_Plane = Z(theta,phi(2));

% Plotting E-Plane = Theta Range at phi = 0

plot(theta,E_Plane);

% Holding on to put the H-Plane on the same grid as the E-Plane

hold on;

% Plotting H-Plane = Theta Range at phi = pi/2

plot(theta,H_Plane);

% Placing a grid on the graph

grid on;

% Title, Axes, and Legends

title('E-Plane (dB) and H-Plane (dB) versus Theta (Radians)');

legend({'E-Plane','H-Plane'},'Location','northwest');

xlabel('Theta (Radians)');

ylabel('Magnitude (dB)');

toc

Elapsed time is 0.343450 seconds.

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Ammar 2024-7-8

在 MATLAB Online 中打开

Hi Voss and Walter,

Thank you for providing this guidance. As far as everything else (plotting, setting the step size for theta, etc), is that meant to be done within the function or outside?

I understand how to "execute the function" F(theta,phi) value. However, I'm trying to extract and then plot specific values for "F".

Would I need to write "seperate" functions for each "task" I'm trying to do: plotting, setting grid size, axes limits, etc? Or can I just write everything into one function?

theta = -pi/2:0.01:pi/2;
phi = [0 pi/2];
E_Plane = F(theta,0);
H_Plane = F(theta,pi/2)
% Then plotting the E-plane and H-plane
plot(theta,E_Plane)
hold on;
plot(theta,H_Plane)
% Other Axis and Grid Settings....
% etc...

Voss 2024-7-8

The function F (or getZ as I called it) would only calculate Z given theta and phi. Everything else would be outside the function, either in a script or in separate functions if you prefer.

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Answer 2

Torsten 2024-7-7

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https://ww2.mathworks.cn/matlabcentral/answers/2135276-error-data-must-be-numeric-datetime-duration-categorical-or-an-array-convertible-to-double#answer_1482386

在 MATLAB Online 中打开

% Declaring Theta and Phi Variables

theta = 0:0.1:pi/2;

% Phi Values

phi_E_Plane = 0;

phi_H_Plane = pi/2;

% Declaring x and y variables as theta and phi

x = @(phi)sin(phi);

y = @(theta)cos(theta);

% Declaring the function Z as a function of theta and phi

F = @(theta,phi)x(phi).^2.*y(theta) + y(theta).^2.*x(phi);

% Calculating E-Plane and H-Plane "values"

E_Plane = F(theta,phi_E_Plane);

H_Plane = F(theta,phi_H_Plane);

% Plotting E-Plane = Theta Range at phi = 0

plot(theta,E_Plane);

% Holding on to put the H-Plane on the same grid as the E-Plane

hold on;

% Plotting H-Plane = Theta Range at phi = pi/2

plot(theta,H_Plane);

% Placing a grid on the graph

grid on;

% Title, Axes, and Legends

title('E-Plane (dB) and H-Plane (dB) versus Theta (Radians)');

legend({'E-Plane','H-Plane'},'Location','northwest');

xlabel('Theta (Radians)');

ylabel('Magnitude (dB)');

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Ammar 2024-7-7

编辑：Walter Roberson 2024-7-8

在 MATLAB Online 中打开

Hello Torsten,

Thank you for the quick response.

My main concern is that my function "Z" is going to grow larger and larger. In other words, its going to be comprised of many different variables and functions that include phi and theta. At that point, I won't be able to "directly" write out the function for "Z".

For example:

x = sin(theta)
y = cos(phi)
a = sin(2*theta)
Y = (a).^2 + (y).^2 + (x).^2 
R = 2*Y + (a).^2 
Z = (R).^2 + (Y).^2 

That's why I used the function "F" to say:

F = @(theta,phi) (Z)

Is there another method to plot "Z" for the specific cases that I have? Thanks.

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Error: Data must be numeric, datetime, duration, categorical, or an array convertible to double.

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Error: Data must be numeric, datetime, duration, categorical, or an array convertible to double.

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