I want to have a 3D polar plot in Matlab. I have a set of cartesian coordinates at points in space and also have corresponding data to plot.
For example, I have 200 numbers of Cartesian (x,y,z) points and 200 numbers of scalar data to be plotted. I tried using patternCustom in Matlab (by converting the cartesian coordinates to spherical polar ones). But it did not help.
The code I used like-
first I save the cartesian coordinates in a column then converting each point to spherical polar by
[az,el,r]=cart2sph(x,y,z);
patternCustom(M,el,az);
Can anyone please help me? thanks
Related
I have a set of data vectors z that has this 2d plot
How would I go about embed this set of data into a 3d plot like this in matlab? I'm asking for advice and suggestions. The theory I'm trying to employ is "for each data vector~zj, “copies” the data vector intothe first two entries of a 3D data vector~yjand then computes the squared length of~zj as the third entry of~yj. " or kernel trick.
Your 2d data will somehow be in the form, that you have x-coordinates and y-coordinates. Let's say you have a vector x and a vector y for simplification.
As you found out the plot3-function proivdes functionality to plot arbitrary points in 3d without the need of generating a mesh. What you need additionally is a third vector z with data for the 3rd dimension.
So what else can you do? The thing I am thinking about is rotating the plane you are plotting you "2d" data:
Rotational matrices can be seen here:
https://en.wikipedia.org/wiki/Rotation_matrix
I have a variable named say P which is simply a n*3 matrix. It stores x,y,z coordinates for a contour plot, its like a closed loop. Now I have several matrices like P which slice my object. What I would like is to create a surface using these contour points. scatter3() does not really give a good representation. The issue using surf() is that since I have contour coordinates, the coordinates are unordered. So the plot obtained using surf() is not the actual closed surface of my figure. How can I resolve this? Let's brainstorm.
I have dataset of XYZ as the coordinates and V as the value at each point (100x4 matrix).
I plot the 3D surface using patch. (by faces & vertices)
How can I plot the contour lines of V (NOT Z) over the 3D surface !?
( The Contour3 function plots 3D contour lines of Z ; But I need contour lines of V. )
Actually I want something like this or this.
Thanks a billion for your help.
Well actually I found out that the isosurface command is exactly what I want.
However, this command requires the V data to be a 3D matrix. But my V is a vector. And the data in it is completely non-uniform and irregular. Now here rises a new question :
How can I convert this non-uniform vector to a 3D matrix, so that it's ready to be used with isosurface command !!?
Please help me with this.
cont3d from MathWorks FileExchange is not exactly what you're looking for, but it may give you some ideas.
I am trying to plot a 3d view of a very large CT dataset. My data is in a 3d matrix of 2000x2000x1000 dimension. The object is surrounded by air, which is set to NaN in my matrix.
I would like to be able to see the greyscale value of the surface of the object (no isosurface) but I cannot quite work out how to do that in Matlab. Can anyone help me please?
Given that I a dealing with a huge matrix and I am only interested in the surface of the object, does anyone know a good trick how to reduce the size of my dataset?
The function surf(X,Y,Z) allows you to plot 3d data, where (X,Y) gives the coordinates in the x-y-plane while Z gives the z-coordinate and the surface color.
By default the function does not plot anything for the NaN entries, so you should be good to go with the surf function.
To set the surf-function to use a grayscale plotting use:
surf(matrix3d);
colormap(gray);
This plots the matrix in a surface plot and sets the colormap to grayscale.
In addition, as I understand your data, you might be able to eliminate entire plane-segments in your matrix. If for instance the plane A(1,1:2000,1:1000) is NaN in all entries you could eliminate all those entries (thus the entire Y,Z-plane in entry X=1). This will however require some heavy for loops, which might be over the top. This depends on how many data matrices you have compared to how many different plot you want for each matrix.
I will try to give you some ideas. I assume lack of a direct 3D "surface detector".
Since you have a 3D matrix where XY-planes are CT scan slices and each slice is an image, I would try to find edges of each slice say with edge. This would require some preprocessing like first thresholding each slice image. Then I can either use scatter3 to display the edge data as a 3D point cloud or delaunay3 to display the edge data as a surface.
I hope this will help you achieve what you are asking for.
I managed to get it working:
function [X,Y,Z,C] = extract_surface(file_name,slice_number,voxel_size)
LT = imread(file_name);%..READ THE 2D MAP
BW = im2bw(LT,1);%..THRESHOLD TO BINARY
B = bwboundaries(BW,8,'noholes');%..FIND THE OUTLINE OF THE IMAGE
X = B{1}(:,1);%..EXTRACT X AND Y COORDINATES
Y = B{1}(:,2);
indices = sub2ind(size(LT),X,Y);%..FIND THE CORRESPONDING LINEAR INDICES
C = LT(indices);%..NOW READ THE VALUES AT THE OUTLINE POSITION
Z = ones(size(X))*slice_number;
I can then plot this with
figure
scatter3(X,Y,Z,2,C)
Now the only thing I could improve is to have all these points in the scatter plot connected with a surface. #upperBound you suggested delaunay3 for this purpose - I cannot quite figure out how to do this. Do you have a tip?
I am trying to create a 2D map of some place. I get a 181x1 vector of laser sensor readings from a robot. All the values in this vector corresponds to a distance from that single angle like 1°,2°..180°. The problem here is I need to create a map by plotting these distances as dots with plot() or a similar function to it.
there is a function for plotting in polar coordinates. try
>> polar( (0:180)/180*pi, distanceVector)
You can convert your angle-distance coordinates to Cartesian X and Y with POL2CART function.
[X,Y] = pol2cart((1:180)/180*pi, distanceVector);
Then you can use PLOT.
plot(X,Y,'.')
plot(theVector, '.')
if you need to plot as dots instead of lines. If the dot is too small, try to plot as circles.
plot(theVector, 'o')
See http://www.mathworks.com/access/helpdesk/help/techdoc/ref/linespec.html for detail.