# Create a surface between two sets of 3d data points

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Matthew Davenport on 19 Apr 2021
Commented: Clayton Gotberg on 20 Apr 2021
Hi,
I have 2 sets of data points that create lines on a 3-Dimensional plot.
I would like create a linear surface between the two sets of data points. Each data point on one set of data would correspond with the data point on the other set. I am unsure of how to go about this other than finding a linear equation for each coupled data points.
r1 = [-2.2607e-05; 1.1301e-08; 1.4319e-04; -1.4319e-04];
x = linspace(0,1000);
y = x;
u1_3 = (r1(1)*x.^2 + r1(2)*y.^3);
figure(3)
hold on
grid on
scatter3(x,y,u1_3-100,'b')
X2 = linspace(0,0);
Y2 = linspace(0,1000);
Z2 = linspace(0,0);
scatter3(X2,Y2,Z2-100,'k')
zlim([-1e3 0])
ylim([-1000 1000])
xlim([-1000 1000])
xlabel('x (meters)')
ylabel('y (meters)')
zlabel('Deflection, m/V')
hold off
Any help on this is much appreciated!
Matthew Davenport on 19 Apr 2021
I would like to show the normal vectors of the surface. The blue set of data represents an actuartor arm position with a surface conected to the black data set.

Clayton Gotberg on 19 Apr 2021
Edited: Clayton Gotberg on 19 Apr 2021
When you send matrices to the plotting command, the way that it plots depends on the orientation of those matrices
% x, y, z already defined as row matrices (1 x n)
X = [x1; x2]; % Create a matrix with x1(1) above x2(1); do the same for Y and Z
Y = [y1; y2];
Z = [z1; z2];
plot3(X,Y,Z) % Result: n lines with two points (x1,y1,z1) and (x2,y2,z2)
plot3(X',Y',Z') % Result: 2 lines with n points
If you are trying to create a surface, specifically, the surf command should take the exact same inputs and create a single surface.
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Clayton Gotberg on 20 Apr 2021
I would guess that the error is because surfnorm needs more information to calculate the normal vector than is present in a 2 x n array. If you want to include the normals, you will probably need to calculate and plot them yourself instead of using that function. I'm also not certain what normal you're looking for as a line has infinite normals. You'd need to define a plane and then either find the normal vector to that plane or find a line perpendicular to the line of interest in that plane.