Solved

Can someone please check my Matlab code to rotate a hyperbola and see what I am doing wrong

Posted on 2009-04-05
7
804 Views
Last Modified: 2016-02-10
Please find the attached pdf tutorial for matlab and multilateration.

page 4. Please see code in the codebox below however when run it does not rotate the hyperbola as per the picture on page 4. It is in a different position?

Why is this?
% Program to plot the hyperbola
% y^2/a^2 - x^2/b^2 = 1
% The hyperbolae are open up/down, so that x is the independent variable
% for plotting. (Using the form x^2/a^2 - y^2/b^2 = 1 requires that y be
% the independent variable, which is awkward programming-wise.)
clear % all variables
figure(1), hold off % start a new figure
set(gca,'FontSize',14) % adjust fontsize
xmax = 30; ymax = 20;
x = linspace(-xmax,xmax,1001);
 
a = 5; b = 3;
theta=60*pi/180; % in radians, 1 radian = 180/pi degrees
xoff=10;
yoff=5;
y=sqrt(((x.^2)./(b^2)+1).*a^2); % corresponding y values
[xout,yout] = xfm1(x,y,theta,xoff,yoff); % rotation and shift
 
plot(xout,yout)
hold on % add to current plot
[xout,yout] = xfm1(x,-y,theta,xoff,yoff); % rotation and shift of negative part
plot(xout,yout) % Plot other half of hyperbola
 
axis([-xmax xmax -ymax ymax]) % specify axis limits
xlabel('x')
ylabel('y')
 
% Add axes
plot([0 0],[-ymax ymax],'k') % y axis
plot([-xmax xmax],[0 0],'k') % x axis
title(['Hyperbola $y^2/a^2 - x^2/b^2 = 1$; $a$ = ', num2str(a), ...
', $b$ = ', num2str(b),';'],'Interpreter','latex')
% Add axes
plot([0 0],[-ymax ymax],'k') % y axis (black line - k)
plot([-xmax xmax],[0 0],'k') % x axis

Open in new window

0
Comment
Question by:jtiernan2008
  • 4
  • 3
7 Comments
 
LVL 15

Expert Comment

by:yuk99
ID: 24073370
I got almost the same figure as on your tutorial with this code without changing anything. I used the same xfm1 function file as we discussed before.
Do you get any figure with this code. If yes, how it's different from what you need? If no, do you get any errors?
0
 
LVL 1

Author Comment

by:jtiernan2008
ID: 24081290
thanks for your response

yes, I know I must be doing something wrong....
please see the attached with the code run and a screenshot from the tutorial.
It appears to not rotate the same.
pic.jpg
0
 
LVL 15

Expert Comment

by:yuk99
ID: 24081361
Change your rotation matrix in xfm1 function. I think we discussed this before. Change the sign for sines.
0
Free Tool: Site Down Detector

Helpful to verify reports of your own downtime, or to double check a downed website you are trying to access.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

 
LVL 15

Expert Comment

by:yuk99
ID: 24081392
0
 
LVL 1

Author Comment

by:jtiernan2008
ID: 24081503
"BTW I think you made a wrong rotation matrix. No, it's correct, but rotate in not usual direction. It should be
xfm = [cos(theta) -sin(theta); ...
      sin(theta) cos(theta"

=> But it is the same as you can see below;
function [xout,yout] = xfm1(xin,yin,theta,x_offset,y_offset)
% Program to rotate and translate x,y values from x",y" to x,y space.
% Written to plot hyperbolas for time of arrival code.
% theta value assumed to be in radians.
 
%  rotation matrix
xfm = [cos(theta) -sin(theta); ...
      sin(theta) cos(theta)];
% make x,y values into a column vector
r_in = [xin; yin];
% rotate 
r_out = xfm*r_in;
x = r_out(1,:); y = r_out(2,:);
xout = x + x_offset; 
yout = y + y_offset;

Open in new window

0
 
LVL 15

Accepted Solution

by:
yuk99 earned 500 total points
ID: 24081599
Usually positive angles rotate counterwise, negative clockwise. If you want opposite direction, just change both sines signes in rotatino matrix, or use negative angle. Again line along y axis has 0 degree.
0
 
LVL 1

Author Closing Comment

by:jtiernan2008
ID: 31566782
thanks a million..
I understand now
0

Featured Post

Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
FizzBuzz challenge 9 82
java continue statement 10 155
bunnyEars challenge 6 138
Work with App store 7 67
Navigation is an important part of web design from a usability perspective. But it is often a pain when it comes to a developer’s perspective. By navigation, it often means menuing. This is less theory and more practical of how to get a specific gro…
This article will show, step by step, how to integrate R code into a R Sweave document
This tutorial will introduce the viewer to VisualVM for the Java platform application. This video explains an example program and covers the Overview, Monitor, and Heap Dump tabs.
The goal of the tutorial is to teach the user how to use functions in C++. The video will cover how to define functions, how to call functions and how to create functions prototypes. Microsoft Visual C++ 2010 Express will be used as a text editor an…

840 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question