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

48 views (last 30 days)
Ammar on 7 Jul 2024 at 22:45
Commented: Voss on 8 Jul 2024 at 3:19
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

Voss on 7 Jul 2024 at 22:55
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');
ylabel('Magnitude (dB)');
toc
Elapsed time is 0.343450 seconds.
Ammar on 8 Jul 2024 at 2:54
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 on 8 Jul 2024 at 3:19
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.

Torsten on 7 Jul 2024 at 22:57
% 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');
ylabel('Magnitude (dB)');
Ammar on 7 Jul 2024 at 23:51
Edited: Walter Roberson on 8 Jul 2024 at 1:08
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.

R2024a

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!