How can I Draw a Line on a 3D plot?

I am trying to draw a red line across a 3D surface plot for an app:

I have the 2D plot coded to do this as follows:

            surf(app.UIAxes2,Bat);
            ylim(app.UIAxes2, [0 60]);
            xlim(app.UIAxes2, [0 60]);
            view(app.UIAxes2,2);
            app.UIAxes2.PositionConstraint = 'outerposition';
            xline(app.UIAxes2,value,'Color','red','LineStyle','-','LineWidth',1.5);

but the xline command will not work for the 3D plot, as it does not follow the Z data and draws a line straight through the dipole I am modelling.

"value" in the above code is whatever line is selected by the app user.

"Bat" is the matrix data I am modelling.

Does anyone know how to plot a red line like this that will contour to my Z data? Here is the code for my 3D plot below:

            surf(app.UIAxes3,Bat);
            ylim(app.UIAxes3, [0 60]);
            xlim(app.UIAxes3, [0 60]);
            view(app.UIAxes3,3);
            app.UIAxes3.PositionConstraint = 'outerposition';
            ztickformat(app.UIAxes3,'%g'); 
            ax = app.UIAxes3;
            ax.ZAxis.Exponent = 0;

Any help is appreciated, thank you.

[Scott MacKenzie]

Have your tried line, instead of xline? It allows for x, y, and z input arguments.

[Joshua Mitchell]

I am trying to use line and it seems like it is possible, but I'm having a hard time figuring out how it should work with my data specifically.

I've tried:

            surf(app.UIAxes3,Bat);
            ylim(app.UIAxes3, [0 60]);
            xlim(app.UIAxes3, [0 60]);
            view(app.UIAxes3,3);
            app.UIAxes3.PositionConstraint = 'outerposition';
            ztickformat(app.UIAxes3,'%g'); 
            ax = app.UIAxes3;
            ax.ZAxis.Exponent = 0;
            line(app.UIAxes3,Bat(value,:),Bat(:,value),Bat(:,10),'Color','red','LineStyle','--','LineWidth',1.5);

And it is giving me strange lines like:

It is probably just how I am setting the x,y,z value but I can't seem to come up with a decent line.

Answer 1

[Scott MacKenzie]

Here's an example using line. I used your code, but re-assigned ax.UIAxes2, Bat, and value so the code would execute on my machine.

UIAxes3 = gca;    % your app.UIAxes3
Bat = peaks; % for testing
value = 30;  % test value

surf(UIAxes3, Bat);
ylim(UIAxes3, [0 60]);
xlim(UIAxes3, [0 60]);
view(UIAxes3, 3);
UIAxes3.PositionConstraint = 'outerposition';
ztickformat(UIAxes3,'%g');
UIAxes3.ZAxis.Exponent = 0;

x = 1:size(Bat,2);
y = ones(1,size(Bat,2)) * value;
z = Bat(value,:);
line(UIAxes3,x,y,z,'Color','red','LineStyle','--','LineWidth',2.5);

[Joshua Mitchell]

This works beautifully when I am plotting a line on my y-axis, but when I try to switch x and y to plot on the x-axis, it plots on the correct line, but it plots the data from the y-axis.

y = 1:size(Bat,2);
x = ones(1,size(Bat,2)) * value;
z = Bat(value,:);
line(app.UIAxes3,x,y,z,'Color','red','LineStyle','-','LineWidth',2.5);

So obviously I can't simply switch these x and y variables so easily as I had naively hoped for, but I'm not sure why. Why would it be any different for me to just switch the axis?

[Scott MacKenzie]

You need to change z as well, to pull z data along the y-axis instead of the x-axis:

z = Bat(:,value);

[Joshua Mitchell]

Of course! Thank you so much, I really appreciate it.

Answer 2

[KSSV]

[X,Y,Z] = peaks(100) ;

% DRaw a line at origin 
x = linspace(-3,3) ;
y = repelem(0,1,length(x)) ;


z = interp2(X,Y,Z,x,y) ; 
% plot 
surf(X,Y,Z)
hold on
plot3(x,y,z,'r','linewidth',3)

[Bretislav Kubes]

Wonderful easy solution, thanks!