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'
Related
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:
I have graphed a Bode plot for my transfer function, and I was wondering if there is some way to insert either horizontal or vertical lines to show a specific value for the gain/phase angle or frequency?
I have found with the following code I can draw a horizontal line on the phase angle graph:
x = linspace(10^-1,10^2,100);
for bleh = 1:length(x)
y(bleh) = -30.9638;
end
bode(num, den)
hold on
plot(x,y)
But this does not seem to apply in the gain graph, nor does my limited knowledge (and only way that makes sense to me) of vertical lines. I tried:
y1 = get(gca,'ylim');
w1 = 1.2;
bode(num, den)
hold on
plot(x,y,[w1 w1],y1)
But I only get the one horizontal line as was done from the above code.
Is this a possibility?
(Using R2017a, if that matters.)
I'm not sure I've understood you question, nevertheless, I propose the following.
When there are more one axes in a figure, as it is the case of the bode diagram, if you want to add something in a specific axes (or in all) you have to specify, in the call to plot the handle of the axes.
So, to add lines in the bode diagram, you have first to identify the handles of the two axes: you can do it in, at least two way:
using the findobj function: ax=findobj(gcf,'type','axes')
extract them as the Children of the figure: ax=get(gcf,'children')
Once you have the handles of the axes, you can get their XLim and YLim that you can use to limit the extent of the line you want to add.
In the following example, I've used the above proposed approach to add two lines in each graph.
The horizontal and vertical lines are added in the middle point of the X and Y axes (problably this point does not have a relevant meaning, but it is ... just an example).
% Define a transfer function
H = tf([1 0.1 7.5],[1 0.12 9 0 0]);
% PLot the bode diagram
bode(H)
% Get the handles of the axes
ax=findobj(gcf,'type','axes')
phase_ax=ax(1)
mag_ax=ax(2)
% Get the X axis limits (it is the same for both the plot
ax_xlim=phase_ax.XLim
% Get the Y axis limits
phase_ylim=phase_ax.YLim
mag_ylim=mag_ax.YLim
%
% Define some points to be used in the plot
% middle point of the X and Y axes of the two plots
%
mid_x=(ax_xlim(1)+ax_xlim(2))/2
mid_phase_y=(phase_ylim(1)+phase_ylim(2))/2
mid_mag_y=(mag_ylim(1)+mag_ylim(2))/2
% Set hold to on to add the line
hold(phase_ax,'on')
% Add a vertical line in the Phase plot
plot(phase_ax,[mid_x mid_x],[phase_ylim(1) phase_ylim(2)])
% Add an horizontal line in the Phase plot
plot(phase_ax,[ax_xlim(1), ax_xlim(2)],[mid_phase_y mid_phase_y])
% Set hold to on to add the line
hold(mag_ax,'on')
% Add a vertical line in the Magnitide plot
plot(mag_ax,[mid_x mid_x],[mag_ylim(1) mag_ylim(2)])
% Add an Horizontal line in the Magnitide plot
plot(mag_ax,[ax_xlim(1), ax_xlim(2)],[mid_mag_y mid_mag_y])
Hope this helps,
Qapla'
I have 32x21 matrix with x axis increment of one parameter (2 to 64 in steps of 2) and y axis increment of n other parameter,in steps of two again. I can plot it as contour plot, but I was wondering if there is a way to have contour plot as animation/movie.Thanks
Did you try to place your plot in a for loop which iterates through all the contours? Use drawnow
e.g.
hold on
for ii = 2:2:64
%do your plotting here
%use "pause" if too fast
drawnow
end
This should update the figure every iteration.
Also see this
I have a figure in which I plot some disperse points and then a trajectory. I want to switch between different trajectories by plotting them in the same figure as the points, but without creating new figures, i.e., "erasing" the first trajectory and then plotting the new one.
Is there a way of doing this?
Perhaps this little demo will be helpful:
xy = rand(20,2);
figure
% Plot first iteration and output handles to each
h = plot(xy(:,1),xy(:,2),'b.',xy(1:2,1),xy(1:2,2),'r-');
axis([0 1 0 1])
% Update second plot by setting the XData and YData properties of the handle
for i = 2:size(xy,1)-1
set(h(2),{'XData','YData'},{xy(i:i+1,1),xy(i:i+1,2)})
drawnow
pause(0.1);
end
You should read up on handle graphics in Matlab and the get and set functions.
All the three variables I am using to plot are matrix of size 1x1x100. I am using this code line to plot:
hold on;
for i=1:100
plot3(R_L(:,:,i),N_Pc(:,:,i),CO2_molefraction_top_of_window(:,:,i),'o');
xlabel('R_L');
ylabel('N_P_c');
zlabel('CO_2')
end
However, I am not getting the third axis, and hence the third variable CO2_molefraction_top_of_window on the plot. May I know where am I wrong?
Besides the above question, but on the same subject, I want to know if there is any option where I can plot 4 dimensional plot just like the 3 dimensional plot which can be drawn using plot3?
So I had the same problem when using plot3. For some reason, using the hold on command "flattens" the plot. I'm not sure why, but I suspect it has something to do with the operation hold on performs on the plot.
Edit: To clarify, the 3d plot is still there, but the perspective has been forced to change. If you use the "rotate 3D" tool (the one with an arrow around a cube), you can see the graph is 3d, the default perspective is just straight on so only two axes are visible and it appears flat.
Just a note --- you only need to do the xlabel ylabel zlabel commands once (outside the loop).
Also:
is there any reason your matrices are 1x1x100 instead of just 100x1 or 1x100?
Because if you reshape them to 2D you can just do the plotting in one hit.
What do you mean by "missing third axis"? When I run your code (or as close as I can get, since you didn't provide a reproducible example), I do get a 3rd axis:
.
X = rand(1,1,100); % 1x1x100 X matrix
Y = rand(1,1,100); % 1x1x100 Y matrix
Z = rand(1,1,100); % 1x1x100 Z matrix
% Now, we could do a for loop and plot X(:,:,i), Y(:,:,i), Z(:,:,i),
% OR we can just convert the matrix to a vector (since it's 1x1x100 anyway)
% and do the plotting in one go using 'squeeze' (see 'help squeeze').
% squeeze(X) converts it from 1x1x100 (3D matrix) to 100x1 (vector):
plot3(squeeze(X),squeeze(Y),squeeze(Z),'o')
xlabel('x')
ylabel('y')
zlabel('z')
This gives the following, in which you can clearly see three axes:
If it's the gridlines that you want to make the graph look "more 3D", then try grid on (which is in the examples in the Matlab help file for plot3, try help plot3 from the Matlab prompt):
grid on
You will have to clarify "missing third axis" a bit more.
I came across a similar problem and as #Drofdarb's the hold on seems to flatten out one axis. Here is a snippet of my code, hope this helps.
for iter = 1:num_iters:
% hold on;
grid on;
plot3(tita0,tita1, num_iters,'o')
title('Tita0, Tita1')
xlabel('Tita0')
ylabel('Tita1')
zlabel('Iterations')
hold on; % <---- Place here
drawnow
end
As opposed to:
for iter = 1:num_iters:
grid on;
hold on; % <---- Not here
plot3(tita0,tita1, num_iters,'o')
title('Tita0, Tita1')
xlabel('Tita0')
ylabel('Tita1')
zlabel('Iterations')
% hold on;
drawnow
end