I have a series of "from" and "to" coordinates in 2D and I would like to draw in matlab a bunch of arrows that begin and end in those coordinates. How do I do that?
I tried champ but that didn't work.
You can draw a single arrox using the annotation function:
h=annotation('arrow',[0 1],[0 1])
for a set of arrows, just loop
You can probably use the quiver plot.
quiver(x,y,u,v)
Plots arrows starting at (x,y) with the direction and length of (u,v). x through v can be vectors of the same length. One arrow is plotted for each of the elements.
Of course you first have to compute the displacement vector (u,v) from your start and endpoints.
Related
I am having real trouble with vectors/matrices etc. in matlab.
I have a 3D vector nxmx2 where n is my x-coordinate, m is my y-coordinate and for each (x,y) there are two z values, the first being my velocity in the x-direction, and the second being my velocity in the y-direction.
How do I plot these velocity functions on a x-y graph? I have been trying with things like:
quiver(A)
quiver(A,A,A(:,:,1),A(:,:,2))
But can't seem to get it to work.
The correct way to use quiver for the input you describe is
quiver(A(:,:,1), A(:,:,2));
If you want the axes of the plot to have equal-spaced values different than 1,2,... you should use meshgrid to generate them, as shown in the examples in the quiver documentation.
I want to plot an inequality in 3d using surf. My condition is
0<=x<=1
0<=y<=1
0<=z<=x/(1+y)
I can create a surface plot using the following commands
[x y]=meshgrid(0:0.01:1);
z=x./(1+y);
surf(x,y,z);
This plot gives me regions where z=x/(1+y) but I am interested in regions where 0<=z<=x/(1+y) over all values of x and y. However, I am unable to plot/color the region explicitly. Can you please help.
A similar question has been asked but there was no acceptable answer and my question is also different.
Using isosurface you can show the boundary. There are two options, first create the points
[X,Y,Z]=meshgrid(0:.01:1);
then plot the boundaries in the z-direction (i.e. Z=0 and Z=X./(1+Y))
isosurface(X,Y,Z,Z.*(X./(1+Y)-Z),0)
or plot all the boundaries (including X=0, X=1, Y=0 and Y=1)
isosurface(X,Y,Z,Z.*(X./(1+Y)-Z).*X.*(X-1).*Y.*(Y-1),0)
All you have to do is come up with a function that is constant on any boundary, its value inside or outside is irrelevant as long as it is not zero.
I am looking for help for my particular problem.
I have a contour plot created from XYZ data. This plot contains 2 broad peaks with one more intense than the other.
When the most intense peak is aligned with the Y axis, I can perform a fitting of every YZ curve at each X values. I usually do a gaussian fit to plot the peak center on the same graph.
In some cases I need to perform the same fitting but no along the Y axis direction (in this case I just plot YZ scan at every different X values) but along another arbitrary direction.
For the moment the only way I found is the following:
-plot the contour plot and find for the position of the most intense peak
-if the position is not aligned with the Y axis, then rotate all the datas and plot again the contour
-perform the YZ gaussian fit for every X value
- Rotate the resulting XY position to go back to the original plot
-plot the XY position as a line on the original contour plot
this is quite long and requires a lot of memory. i would like ot know if there is a more elegant/faster way.
Thanks for your help
David
I take it you want to extract data from the (x,y,z) data along some arbitrary line in order to make a fit. A contour plot will show only part of the data, the full z(x,y) data can be shown with imagesc etc. Say you want the data along line defined by two points (x1,y1) -> (x2,y2). According to the eq of the line, the line y=a*x+b the slope a is (y2-y1)/(x2-x1) and b=y1-a*x1. For example, I'll select (x,y) coordinates in the following contour:
Create data and end points:
m=peaks(100);
x1=11 ; x2=97;
y1=66; y2=40;
Thus the line parameters are:
a=(y2-y1)/(x2-x1);
b=y1-a*x1;
and the line is:
x=x1:x2;
y=round(a*x+b);
select the proper (x,y) elements using linear indexing:
ind=sub2ind(size(m),y,x)
plot:
subplot(2,1,1)
contour(m,10); hold on
line([x1 x2],[y1 y2],'Color',[1 0 0]);
subplot(2,1,2)
plot(m(ind))
You can now use vec=m(ind) to fit your function.
I have a 2D scatter plot in MATLAB. Is it possible to interpolate the scatter plot to create an area plot?
If you're simply trying to draw one large filled polygon around your entire set of scattered points, you can use the function CONVHULL to find the convex hull containing your points and the function PATCH to display the convex hull:
x = rand(1,20); %# 20 random x values
y = rand(1,20); %# 20 random y values
hullPoints = convhull(x,y); %# Find the points defining the convex hull
patch(x(hullPoints),y(hullPoints),'r'); %# Plot the convex hull in red
hold on; %# Add to the existing plot
scatter(x,y); %# Plot your scattered points (for comparison)
And here's the resulting figure:
Scatter is generally used to represent data where you can't use a line graph, i.e., where each x might have many different y values, so you can't convert directly to an area graph--it would be meaningless. If your data actually is representable as a line graph, then pass it to area directly.
So I'm not quite sure what you want, but here are some possibilities:
You could create a Voronoi diagram based on your points. This will show a region near your points showing which points are closer to a specific point: voronoi(x,y), or see the help.
You could bucket or quantize your data somehow, making it fit into a grid, and then plot the grid. This could also be considered a histogram, so read up on that.
You could just use larger scatter markers (scatter(x,y,scale) where scale is the same dimensions as x and y).
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.