I'm trying to graph a solution obtained through the quadratic formula in Matlab. Since it's obtained by the quadratic formula, there are two parts: plus and minus. The graph should be a hyperbola. How can I place the upper part and the bottom part on the same graph?
There are different ways. Let's say you want to plot the solution of y^2 = x, that is y = ±sqrt(x):
You can plot the two parts with the same color using a plot once…
x = 0:0.1:10;
plot(x, sqrt(x), 'k', x, -sqrt(x), 'k')
…or twice:
x = 0:0.1:10;
plot(x, sqrt(x), 'k')
hold on
plot(x, -sqrt(x), 'k')
hold off
Or you can plot everything in one go like you might draw it with a pen:
x = [10:-0.1:0 0.1:0.1:10];
y = [-sqrt(10:-0.1:0) sqrt(0.1:0.1:10)];
plot(x, y)
Related
I have three matrices x, y, z which are plotted via scatter3 in matlab. However I also need vertical lines dropping from every point in the graph for better visualization.
Using matlab 2017a, implemented 3D scatter plot in matlab.
enter code here
clc;
figure
x = [0,0,0,0,0,10,10,10,10,10];
y = [0,10,20,30,40,-10,0,10,20,30];
z = [46,52,51,59,53,85,56,87,86,88];
scatter3(x, y, z, 30, 'filled')
You could also use the built in function stem, which is doing exactly that.
The minor trick is that you cannot pass the z coordinates in the shorthand form stem(x,y,z), but the graphic object still accept z data, you just have to send them as additional parameter.
The nice part of it is you do not need a loop ;-)
x = [0,0,0,0,0,10,10,10,10,10];
y = [0,10,20,30,40,-10,0,10,20,30];
z = [46,52,51,59,53,85,56,87,86,88];
hp = stem(x,y,'filled','ZData',z) ;
Or as Gnovice nicely pointed out, even easier to use the stem3 function which accept z data directly:
hp = stem3(x,y,z,'filled') ;
Both example above will produce:
As #SardarUsama pointed out, plot3 should do the trick. Code could be more compact but kept it as is for clarity.
% MATLAB R2017a
x = [0,0,0,0,0,10,10,10,10,10];
y = [0,10,20,30,40,-10,0,10,20,30];
z = [46,52,51,59,53,85,56,87,86,88];
figure
scatter3(x, y, z, 30, 'filled') % scatter plot (3D)
zRng = zlim;
hold on
for k = 1:length(x)
xL = [x(k) x(k)];
yL = [y(k) y(k)];
zL = [zRng(1) z(k)];
plot3(xL,yL,zL,'r-') % plot vertical line (3D)
end
I have the following script:
close all; clear all; clc;
x = linspace(-2*pi,2*pi);
y = linspace(0,4*pi);
[X,Y] = meshgrid(x,y);
Z = sin(X)+cos(Y);
values = -10:0.5:10;
figure
[C,hh] = contour(X, Y, Z, values,'r', 'LineWidth',1);
clabel(C, hh, values, 'fontsize',7)
As you can see in the contour lines, all of the lines are plotted with LineWidth = 1. I would like to plot special line for the value = 0, with LineWidth = 2, how to set it? Thanks a lor for your help.
You will need to make a secondary contour plot to highlight the desired contour levels. The MathWorks has an example of this in the documentation.
For your case we'll have something like the following:
% Generate sample data
x = linspace(-2*pi,2*pi);
y = linspace(0,4*pi);
[X,Y] = meshgrid(x,y);
Z = sin(X)+cos(Y);
values = -10:0.5:10;
% Generate initial contour plot
figure
[C,hh] = contour(X, Y, Z, values,'r', 'LineWidth',1);
clabel(C, hh, values, 'fontsize',7)
% Generate second contour plot with desired contour level highlighted
hold on
contour(X, Y, Z, [0 0], 'b', 'LineWidth', 2);
hold off
Which returns the following:
Not that I've specified the single contour level as a vector. This is explained by the documentation for contour:
contour(Z,v) draws a contour plot of matrix Z with contour lines at the data values specified in the monotonically increasing vector v. To display a single contour line at a particular value, define v as a two-element vector with both elements equal to the desired contour level. For example, to draw contour lines at level k, use contour(Z,[k k])
If you want to highlight multiple levels then this does not apply (e.g. contour(X, Y, Z, [-1 0], 'b', 'LineWidth', 2) to highlight -1 and 0)
I would like to plot this function of Two Variables you can find it here
$$z^2=t(t-i) \Longleftrightarrow x^2+y^2=4x^2y^2 \Longleftrightarrow y=\dfrac{\pm x}{\sqrt{4x^2-1}} \mbox{ with } |x|>\frac{1}{2}$$
would someone show me step by step how to plot this in matlab
is there any script or toolbox in http://www.mathworks.com/matlabcentral/fileexchange
which make plot of that kind of curves quickly
this is by geogebra
This is by wolframe
You can use symbolic variables with ezplot.
syms x y % makes symbolic variables
h1 = ezplot('-4*x^2*y^2+x^2+y^2'); % plots the equation
axis equal
set(h1, 'Color', 'k');
Or you can define a function,
f = #(x,y) -4.*x.^2.*y.^2+x.^2+y.^2;
h1 = ezplot(f);
set(h1, 'Color', 'k');
It won't be easy to have the axis in the middle, I hope it's not necessary to have that.
Edit
You can download oaxes here
syms x y
h1 = ezplot('-4*x^2*y^2+x^2+y^2');
axis equal
set(h1, 'Color', 'm');
oaxes('TickLength',[3 3],'Arrow','off','AxisLabelLocation','side',...
'LineWidth',1)
Edit
For 3D plot try this,
% First line provides a grid of X and Y varying over -5 to 5 with .5 as step-size
[X,Y] = meshgrid(-5:.5:5);
% instead of "=0", Z takes the values of the equation
Z = -4 .* X.^2 .* Y.^2 + X.^2 + Y.^2;
surf(X,Y,Z) % makes a 3D plot of X,Y,Z
You can also try contourf(X,Y,Z) for 2D plot.
If I have a curve plotted in an axis is there a way of copying the curve and plotting next to it without running the function.
I.e. I have a code to plot a function from -1 to 0, I dont want the function to be correct from 0 to 1, I simply want to replicate the curve next to it.
Sorry for vague question but Im at a loss here
Using the function sin(x) as an example, you could do this
x_min = -1;
x_max = 0;
x = x_min:0.1:x_max;
y = sin(x);
hold on
plot(x, y, 'LineWidth', 1.2)
plot(x + x_max - x_min, y, 'LineWidth', 1.2)
plot([x_max x_max], [sin(x_min) sin(x_max)], 'k--')
axis equal
to get the following
I'm trying to plot a 3D surface in Matlab and I want to "compress" the plot a little bit in the z dimension. Now the lengths of x, y and z axes are the same, and the plot looks like a cube. I'd like it to look flatter in the z dimension, without altering the axes limits.
Is there any easy way to achieve this?
Try fiddling with the DataAspectRatio and the PlotBoxAspectRatio properties of the axes, which may also be controlled by the pbaspect and daspect commands, correspondingly.
Example
%// Plot surface
[X, Y] = meshgrid(-10:.1:10, -10:.1:10);
Z = 100 - X .^ 2 - Y .^ 2;
surf(X, Y, Z, 'EdgeColor', 'None')
%// Flatten the z-axis a bit
pbaspect([1 1 .2])
daspect([1 1 50])
Original plot:
Flattened plot: