Suppose I have a set of points [x1,x2,...,xn] then how do I plot them on the real line? . The reason I am asking is that I want to plot the eigen values of a Gaussian Orthogonal Ensemble along the x axis. So using eig(A) , I get an array of size n(lets say 10) . So I want to plot those 10 points along the x axis. That is I simply want to plot these real numbers on the x-axis. It does not matter if I plot it on say the line y=1 . Given a pen and paper , I would just draw a line and mark them with dots. How do I do this on MATLAB?
Put even simply , I just want to plot [1,2,3,4,5] on the x axis with prominent dots.
So what I would ideally want is a prominent axis and prominent dots on it according to [x1,...,xn] and also display the labels .
Here is a picture
What I have tried is
x=[1,2,3,4]
plot(x,0) or plot(x,1). But it shows just a blank graph. Can anyone help me out with this? I am an absolute noob in MATLAB.
I was expecting the line y=0 or y=1 with dots marking the points (1,0),(2,0),(3,0),(4,0) or (1,1),...,(4,1).
" I was expecting the line y=0 or y=1 with dots marking the points (1,0),(2,0),(3,0),(4,0) or (1,1),...,(4,1)."
The following script will do that:
hold('on') % Do all plots in the same figure
axis([0,5,-0.1 1.1]);grid('on') % Set the axes and turn on the grid
x = 1:4 % x = [1 2 3 4]
plot(x,ones(size(x)),'b') % Line y=1
plot(x,zeros(size(x)),'b') % Line y=0
scatter(x,zeros(size(x)),'MarkerFaceColor','b') % Points: (1,0),(2,0),(3,0),(4,0)
scatter(x,ones(size(x)),'MarkerFaceColor','b') % Points: (1,1),(2,1),(3,1),(4,1)
The result:
Related
I am trying to generate a random rotation matrix R and apply it to a vector. At the end, I have to plot both the original vector and the vector after rotation. The original vector has to be plotted with black dashed line, and the vector after rotation has to be plotted with black dotted line. I have done every step correctly except I can't plot the vector after rotation with dots. MATLAB plots only the beginning and last points of the vector, but not fully. Interestingly if I try 'k--' instead of 'k.' it works correctly. Can somebody show what I am missing here?
% rand(3,1) generates a random 3 by one column vector. We use this u to plot
u=rand(3,1)*2-1;
% plot the origin
plot3(0,0,0,'.k')
% axis setting
axis vis3d
axis off
%%%%% your code starts here %%%%%
% generate a random rotation matrix R
[R,N] = qr(randn(3));
% plot the x axis
plot3([0,1],[0,0],[0,0],'r');
text(1,0,0,'x')
% plot the y axis
plot3([0,0],[0,1],[0,0],'g');
text(0,1,0,'y')
% plot the z axis
plot3([0,0],[0,0],[0,1],'b');
text(0,0,1,'z')
% plot the original vector u
plot3([0,u(1)],[0,u(2)],[0,u(3)], 'k--');
text(u(1),u(2),u(3),['(',num2str(u(1),'%.3f'),',',num2str(u(2),'%.3f'),',',num2str(u(3),'%.3f'),')'])
hold on
% apply rotation and calcuate v plot the vector after rotation v
v = R*u;
% plot the new vector v
plot3([0,v(1)],[0,v(2)],[0,v(3)], 'k.');
text(v(1),v(2),v(3),['(',num2str(v(1),'%.3f'),',',num2str(v(2),'%.3f'),',',num2str(v(3),'%.3f'),')'])
%%%%% your code ends here %%%%%
I replaced 'k.' with ':k' and it worked like a charm. However, I don't have any idea about what is going on. Why didn't 'k.' work which?
The documentation on plot() clearly specifies this:
. Point
-. Dash-dot line
: Dotted line
Thus k. makes only a black dot as marker (i.e. on the exact points you specified as (x,y,z) coordinates), whereas k: makes a dotted line appear from point to point.
The same syntax works for other plotting commands where you can specify line styles, such as plot3D().
I am a new user of not only Matlab but stackoverflow. I am looking for an information as I just started using Matlab. I went through basic commands of matlab but I am not getting an idea of how to work with below problem statement.
I want to create the below graph
There are two lines and the angle between them is variable from zero degree till 30 degree and the length of lines can be taken anything.
It will be helpful if anyone lets me know how to create the above figure in matlab.
Thanks
Since you want to plot a line, you just need to define the (x,y) coordinates of the starting and ending point of the line itself
For a given angle theta and a given starting point, you can define coordinates of the line using sin and cos functions (sind and cosd if theta is in deg):
x_start=1;
y_start=3;
x_coord=[x_start x_start+r*cosd(theta)]
y_coord=[y_start y_start+r*sind(theta(i))]
In your case, you can use a for loop to generate all the lines with theta ranging from 0 to 30°.
This is a possible implementation: at each iteration of the for loop, a line is plotted and displayed for 1 sec than it is deleted.
% Define the length of the line
r=3;
% Define the starting point coordinates
x_start=1;
y_start=3;
% Define the set of angles (in radiants)
theta=[0:30];
% Open a Figure
figure
% Add the axes
axes
daspect([1 1 1])
hold on
% Plot the reference line
x_ref=[x_start r+x_start]
y_ref=[y_start y_start]
xlim([0 r+x_start])
ylim([0 r+y_start])
plot(x_ref,y_ref,'--b','linewidth',2)
grid minor
% Plot the line
for i=1:length(theta)
% Plot the line
pl_h=plot([x_start x_start+r*cosd(theta(i))], ...
[y_start y_start+r*sind(theta(i))],'r','linewidth',2)
xlim([0 r+x_start])
ylim([0 r+y_start])
% Add a string displaying the value of the current angle
tx_h=text(1,2,['Angle= ' num2str(theta(i)) ' [Deg]'])
pause(1)
delete([tx_h pl_h])
end
Hope this helps,
Qapla'
Say I have a matrix hey 15x15. I want to plot the value of the matrix as a 2D plot for better visualization. But Matlab plots with the convention that origin is in bottom-left corner and positive x is along the left and positive y is along the up direction from origin.
but i want to make my plots such that origin is in top-left corner, +ve x is left and +ve y is down.
So i just used a slight trick.
figure
axis([0 15 -15 0]);
daspect([1,1,1])
hold on
rectangle('Position',[3,-6,2,3],...
'EdgeColor','black',...
'LineWidth',2,...
'FaceColor','cyan')
for i=1:nrows
for j=1:ncolumns
if char(hey(i,j))=='^'
text(j,-i,'^');
elseif char(hey(i,j))=='>'
text(j,-i,'>');
elseif char(hey(i,j))=='v'
text(j,-i,'v');
elseif char(hey(i,j))=='<'
text(j,-i,'<');
end
if obstacle(i,j)==1
text(j,-i,'X');
end
end
end
text(goalY,-goalX,'T');
I made the transformation (x,y)-->(y,-x). But the downside is that the axes are then numbered along y as -1 to -15. However if reader was following above, i only wanted to plot the matrix values and in matrix the y runs +ve downwards from 1 to 15 for my case.
So i want the plot to show +1 thru +15 along y with origin at top-left and x graduated as it is but the values +1 to +15 written at the top of the plot rather than below.
How to do this? In the extreme case, i am alos willing to transfer the matrix hey to another software that can do the nice plot as i want. If any of the two alternatives is possible, please give concrete steps to do it.
EDIT:
After using the helpful methods below, i still have to use a trick like plot (j,i) instead of the innocent plot(i,j). This is because for matrix (i,j) is mapped to graph plot (x,y) as x=j, y=i. Is there a similar workaround? a matrix element is (row #, column #). But in 2D matlab graph, we will denote it's position as (column #, row #). I was just guessing if there was some matlab in-built function to take care of this. like i will give it (row #, column #) but matlab will plot (column #, row #). Is there such a function?
I think axis ij does what you want:
axis ij places the coordinate system origin in the upper left corner. The i-axis is vertical, with values increasing from top to bottom. The j-axis is horizontal with values increasing from left to right.
To locate the x axis on top, change the 'XAxisLocation' of the axes to 'top' (default is 'bottom').
Example:
x = 1:10;
y = x.^2;
plot(x,y)
axis ij
set(gca,'XAxisLocation','top')
Original plot (lines 1-3 of above code):
After axis ij (line 4):
After set(gca,'XAxisLocation','top') (line 5):
If I followed correctly you are looking for the axes XAxisLocation and YDir properties. You can set them to top and reverse respectively to get the output you want. You can also set the XTick property to 1:15 to show every value from 1 to 15.
Example:
clear
clc
%// Create dummy data
[x,y] = meshgrid(1:15,1:15);
u = cos(x).*y;
v = sin(x).*y;
figure
quiver(x,y,u,v)
set(gca,'XAxisLocation','top','XTick',1:15,'YDir','reverse')
hold on
%// I changed the coordinated of the rectangle to fit with the change in
%y-axis.
rectangle('Position',[3,3,2,3],...
'EdgeColor','black',...
'LineWidth',2,...
'FaceColor','cyan')
axis([0 15 0 15])
Which gives the following:
I would like to plot a line, and in grey-shaded X% deviation of a signal, in MATLAB. Then, I'd plot another signal and see (visually) how much of the second signal is outside the gret-shaded area.
The task I'd like to get help done is the shaded area: similar to the image attached below.
I am aware of similar solutions with errorbar, but I think this is a much clearer plot to visualize.
If for example I had:
x = 0:0.1:10;
y = 1 + sin(x);
What would the 5% grey-shaded plot of y look like? (that area?)
See this answer for an example: MATLAB fill area between lines
Do you have the error of y at each sample in x? Let's assume you have and the upper bound is in variable yu and the lower bound in variable yl. Then you could plot it using:
x = 0:0.1:10;
y = 1 + sin(x);
% I create some yu and yl here, for the example
yu = y+.1;
yl = y-.1;
fill([x fliplr(x)], [yu fliplr(yl)], [.9 .9 .9], 'linestyle', 'none')
hold all
plot(x,y)
fill(X,Y,ColorSpec,...) plots a polygon with edges specified in the first two parameters. You have to fliplr (flip left-right) the arrays, so that it correctly draws the shape of the area to be filled 'in a circle' around it. The [.9 .9 .9] is the colour specification, in this case a light grey. I removed the edge by setting no line, to make it even more similar to your desired plot. One detail: plot the filled area before plotting y, because the last plotted object goes on top of the others.
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.