I have a problem plotting a 3D plot of my transfer function. In matlab I have tryed this:
[T,w] = meshgrid(1:1:32,1:1:100);
sys2=20*log((1-w.*(T./2)./w.*T).*(((2.56.*(w.^2)+1.6.*w+1)./(0.0008.*(w.^6)+0.0124.* (w.^5)+0.173.*(w.^4)+(w.^3)))./1+(((2.56.*(w.^2)+1.6.*w+1)./(0.0008.*(w.^6)+0.0124.*(w.^5)+0.173.*(w.^4)+(w.^3))))));
surf(T,w,sys2);
But I get this error:
??? Error using ==> surf at 78
X, Y, Z, and C cannot be complex.
What could be wrong please?
Or can anyone tell me how to plot this in Mathcad?
Thank you.
You can't plot a complex number versus two independent variables -- you would need four axes.
What you can do is:
Use two separate figures (or two subplots in the same figure) to plot real part and imaginary part. In Matlab,
surf(T,w,real(sys2));
figure %// create new figure for the other graph
surf(T,w,imag(sys2));
Alternatively, plot absolute value and phase:
surf(T,w,abs(sys2));
figure %// create new figure for the other graph
surf(T,w,angle(sys2));
A more exotic possibility is to use z axis for absolute value and colour for phase, in the same graph:
surf(T,w,abs(sys2),angle(sys2)); %// fourth argument of surf specifies colour
Related
I have multiple theta and rho stored as matrices in variable out. I want to plot all of them using polar function in Matlab R2015b.
I'm new to Matlab and so far I did this :
subplot(1,3,1)
polar(out(1),out(2),'*')
subplot(1,3,2)
polar(out(3),out(4),'*')
subplot(1,3,3)
polar(out(5),out(6),'*')
I've two questions:
How can I combine them into a single polar plot, i.e one figure instead of three with '*' position intact ?
How can I remove the lower part of polar plot so that I can have a semicircle instead of full plot? Is it possible to customize polar plot labels like removing the degree labels?
Use the commmand hold on (and get rid of the subplots) or
Plot everything together with polar(out(1:2:end),out(2:2:end),'*')
Use the ylim([-0.5 0]) command see this answer.
I want to graph different ellipses at different heights (z-coordinates).
My idea was to write the following code:
z=0:1/64:3/8;
t=linspace(-pi,pi,25);
[t,z]=meshgrid(t,z);
x=cos(-t);
y=cos(-t-4*pi*z);
I would like MATLAB to read my code like:
"Find x and y, and plot at the corresponding height (z). By doing so, join the points such that you'll form an ellipse at constant z".
I'm not sure what kind of function I could use here to do this and was hoping for someone to tell me if there exists such a function that will do the job or something similar.
In case you're wondering, I want to graph the polarization of light given two counterpropagating beams.
EDIT: While this is similar to the question draw ellipse and ellipsoid in MATLAB, that question doesn't address plotting 2D ellipses in 3D axes, which is what I am trying to do.
This can be solved by removing the meshgrid, and just using a plain old for-loop.
t = linspace(-pi,pi,25);
z = 0:1/64:3/8
f = figure;
hold on;
for i = 1:length(z)
x=cos(-t); y=cos(-t-4*pi*z(i));
plot3(x,y,z(i)*ones(length(z),1));
end
The problem in the original code is that you're trying build the ellipses all at once, but each ellipse only depends on a single z value, not the entire array of z values.
When I run this code, it produces the following plot:
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'm trying to do a wedge plot (right ascension vs redshift). I was thinking I could use a scatter plot in polar coordinates. The polar function in matlab seems very limited. Even this
polar(a(:,1),a(:,2),'Linewidth',1)
gives me an error:
Error using polar (line 23)
Too many input arguments.
Is there a simple way to achieve what I want using Matlab? Do you know of another software that would do it easily?
Thanks,
Mike
Matlab is quite adequate for that, I think.
As for the polar function, it seems it doesn't allow properties (such as 'linewidth') to be specified directly. But you can get a handle to the created object and then set its 'linewidth', or other properties:
h = polar(a(:,1),a(:,2));
set(h,'linewidth',1)
If you want a scatter plot, maybe you'd prefer not to have lines, but instead to plot a marker (such as a dot) at each point:
h = polar(a(:,1),a(:,2),'.');
set(h,'markersize',12)
Example:
To see a list of properties that you can set, as well as their current values, type
get(h)
I am trying to plot on the same figure the evolution of a function f, with argument x in ]0,1]. I would like to see both the evolution of f far away from 0 and close to 0, on the same figure, with one x axis.
For now I only have two different figures, one using plot with x=[0.1 ... 1], and one using semilogx with x=[1e-9 1e-7 1e-5... 0.1]. I would like to have both graphs on the same figure, with the x axis being logarithmic at the beginning, then linear after a certain x0 (let's say x0=0.1).
I do not want something using plotxx since I want only one x axis.
Do you know if this is possible?
Thank you for your time and help.
Just plot your y vector without specifying the x vector, this will get you a uniformly spaced plot, then use XTick and XTickLabel to make it work. For example,
x1=logspace(-10,-1,10);
x2=linspace(1,10,10);
y1=x1.^0.25;
y2=1./x2;
plot([y1 y2],'-x')
xlabels=num2cell([x1 x2]);
set(gca,'XTick',1:numel(x1)+numel(x2),'XTickLabel',xlabels)
If you want to use Latex to format tick labels, you'll need to download a function from the Matlab File Exchange.