I am conducting an experiment regarding the detection of movement using a shimmer device (X, Y, Z axis).
If the person is lying on the ground, is this the X, Y or Z axis?
Related
If I have this code
plot(X, Y, 'rx')
How do I add a custom label for each of these (X, Y) coordinates which would display next to the red x on the figure?
I have an array with 4 columns:
x coordinates,
y coordinate,
z coordinate,
and velocity magnitude.
Is there a simple way to convert this data to a heat map?
Thanks.
Try using scatter3:
scatter3(x, y, z, 20, v);
colormap jet
I have calibrated my camera and I have now cameraParams, rotation and translation matrices (R ,t)
I know that there is a way to get the world coordinates from the pixel indices by the function "pointsToWorld(__)" but I want to do the otherwise , I can't find anything about that in the Matlab help !
So I don't know what to do, any suggestions?
Currently you have to do that yourself. If you have R and t, you can use the cameraMatrix function to compute the camera projection matrix P. Then you can compute the projection of a world point into the image as follows:
P = cameraMatrix(cameraParams, R, t);
p = [X, Y, Z, 1] * P;
x = p(1) / p(3);
y = p(2) / p(3);
X, Y, and Z are the world coordinates. x and y are the image coordinates in pixels.
I have a function and want to plot it on cylindrical coordinate.
w(z,theta)=sin(n.pi.z/a).sin(m.theta)
The limits of variables are: z=0..a , theta=0..theta_0 and radius of cylinder is R=1.
As a physical sense I can explain that if we in the Cartesian coordinate,
z & theta are x,y axis and w is surface on this rectangular domain. But in cylindrical coordinate z & theta restrict one cylindrical piece of cylinder with radius=1 that w is surface on this domain.
Plotting using cylindrical or spherical coordinates involves several steps:
Create vectors for theta and z:
theta = linspace(0,2*pi);
z = linspace(0,10);
Create a meshgrid from theta and z:
[TH,Z] = meshgrid(theta,z);
Write your function R(TH,Z):
R = sin(Z)+1+5*sin(TH); %// For cylinder it would be simply R = ones(size(Z));
Convert cylindrical coordinates to cartesian:
[x,y,z] = pol2cart(TH,R,Z);
Plot the result using surf, mesh or whatever:
mesh(x,y,z);
axis equal
This is the result you get:
How can I plot a 3D-plane at specific point in Matlab?
Consider the plane equation
Z=(-a * X - b * Y)/c
with following coefficients:
a=0.01; b=0.03; c= 1; d=0.
I want to plot this plane around point (100,100) not at origin (0,0). How it possible to do that?
The code I used:
[X,Y] = meshgrid(x);
a=0.1;
b=0.2;
c=1;
d=0;
Z=(-a * X - b * Y)/c;
surf(X,Y,Z)
shading flat
xlabel('x')
ylabel('y')
zlabel('z')
surf() just plots whatever set of points you give it. To generate those points, you're evaluating the equation at a specific set of coordinates given by X and Y. Therefore you want those points to be centred around the region of interest:
[X, Y] = meshgrid(95:0.1:105); % e.g. +/-5 at resolution of 0.1
or, say, for arbitrary view coordinates m,n:
[X, Y] = meshgrid(m-20:m+20, n-20:n+20); % e.g. +/-20 at resolution of 1
That gives you the view around 100,100 of a plane centred at the origin, which I think is what you're asking for.
Alternatively if you want the plane itself centred at 100,100, then you need that offset in the equation:
Z=(-a * (X - 100) - b * (Y - 100))/c;
so then a view centred on the origin will be equivalent to viewing the original plane around -100,-100.