Add plot to an existing surface

Hi, i have a surface made with curve fitting tool. Now i'd like to add a 3d line to the same plot to see the intersection point between the line and the surface. Is it possible? thanks

Answer 1

[Vedant Shah]

Hi @Giuseppe Giaquinta,

To add a 3D line to a plot that features a surface generated using the Curve Fitting Tool in MATLAB, the “hold” function can be utilized. To find the intersection point between the line and the surface, the “feval” function can be used. For further details on these functions, please refer to the MATLAB documentation using the following commands in the MATLAB command line window:

web(fullfile(docroot, '/matlab/ref/hold.html')) 
web(fullfile(docroot, '/matlab/ref/feval.html')) 
web(fullfile(docroot, '/optim/ug/fsolve.html')) 

Below is a sample code snippet that demonstrates how to achieve the desired functionality:

% Assuming `fittedmodel` is your generated fit function 
[fitresult, gof] = fittedmodel(X, Y, Z); 
hold on; 

% Define the line 
t = linspace(-5, 5, 1000); 
x_line = t; 
y_line = t; 
z_line = 7*t + 1; % Example line: z = 2*x + 1 

% Plot the line 
plot3(x_line, y_line, z_line, 'r', 'LineWidth', 2); 
hold off; 

% Define the intersection function 
intersection_func = @(t) feval(fitresult, t, t) - (7*t + 1); 

t_intersect = fsolve(intersection_func, 0); % Initial guess at t = 0 

% Calculate intersection coordinates 
x_intersect = t_intersect; 
y_intersect = t_intersect; 
z_intersect = 7*t_intersect + 1; 

% Plot the intersection point 
hold on; 
plot3(x_intersect, y_intersect, z_intersect, 'ko', 'MarkerSize', 15, 'MarkerFaceColor', 'g'); 
hold off; 

disp(['Intersection Point: (', num2str(x_intersect), ', ', num2str(y_intersect), ', ', num2str(z_intersect), ')']); 

It is assumed that the plot generated using the Curve Fitting Tool is saved in a MATLAB file as “fittedmodel.m”. The above code plots the line using “plot3” function and then employs the “feval” function to find the intersection point.

The result obtained using a sample dataset is illustrated below:

In the sample output, the green point at the center represents the intersection point.

[Giuseppe Giaquinta]

Hi Vedant, thank you so much for your precious support, you are really kind.

This is an 11 year old question, but I appreciate the answer even though I don't even remember how to install matlab anymore!