I want to rotate a 2d array by a certain angle. I can use teh rot90 command and rate 90 degrees but I'm not able to figure out a way to rotate it by like say 60degrees..

12/3/2008 8:49:37 AM

multiply the rot90 command by 2/3 to get your 60° rotation

12/3/2008 9:40:59 AM

You realize that rot90 physically rotates the matrix? Like if you had written it on paper and then rotated the paper 90 degrees.

|1 2 3|
|4 5 6|

it would return

|3 6|
|2 5|
|1 4|

In short there is no such thing as rotating it anything other than a factor of 90deg.

So I assume you are rotating a vector? If so then you multiply by the rotation matrix IIRC.

12/3/2008 10:01:45 AM

^ yea thats what I meant..how do I get teh IIRC thing?

12/3/2008 10:51:50 AM

you know iirc = if i remember correctly, right?

12/3/2008 11:00:26 AM

12/3/2008 11:04:42 AM

Yea I'm sure googling "rotation matrix iirc" didn't help you much so:

http://mathworld.wolfram.com/RotationMatrix.html

12/3/2008 11:08:05 AM

Quote :

"yea thats what I meant..how do I get teh IIRCrotation matrix thing?"

use math?

Looks like matlab has this built in though... nice

[Edited on December 3, 2008 at 11:47 AM. Reason : ]

12/3/2008 11:45:55 AM

If you have the image processing tool box the imrotate command should do what you want.

Quote :

"B = imrotate(A,angle) rotates image A by angle degrees in a counterclockwise direction around its center point. To rotate the image clockwise, specify a negative value for angle. imrotate makes the output image B large enough to contain the entire rotated image. imrotate uses nearest neighbor interpolation, setting the values of pixels in B that are outside the rotated image to 0 (zero)."

12/3/2008 12:00:51 PM

robotics toolbox has them too

rotx, roty, and rotz

12/3/2008 12:11:26 PM

I have another question.. does anyone here know how to solve second order differential equations in Matlab? I need to solve three 2nd order equations.. I've broken them down to six 1st order equations and solved them.. m not sure if my solution is right..

1/14/2009 11:14:49 AM

^ Look under MATLAB help in the following section:
MATLAB -> Mathematics -> Differential Equations -> *

All the functions available to you, their syntax, and how to apply them to your particular types of equations is all spelled out in great detail.

1/14/2009 12:38:16 PM