Newbie question - Error in line 2

Sorry to ask a really newbie question. Does anyone know why the attached does not work?

[Star Strider]

It appears that you are coding your own rotation matrix. I do not see any obvious errors.

I cannot run an image of your code, only posted and properly formatted code, so I cannot test it.

How are you calling it?

What about it is not working?

[Jim Riggs]

I see an error. See my comment, below.

Answer 1

[Walter Roberson]

The error message itself did not get included, but I suspect that you tried to click Run to run the code. You need to save the file and then invoke the code from the command line, providing a value for the argument. For example,

AbvMa(pi/7)

[Jonas Persson]

Thanks! When i try that the following happens:

[Walter Roberson]

That line does not go into the file. You need to enter that at the command prompt.

[Jonas Persson]

I am extremely grateful for the answer and sorry for being such a newbie. Could you help me with the syntax? I will not ask any more after that..

[Image Analyst]

Get rid of the line

>> y = AbvMa(pi/7)

from your m-file, and call that from the command line.

y = AbvMa(pi/7)

Or else put it at the very top of the m-file, above the function line.

Answer 2

[Jim Riggs]

Your equation set looks like it produces a direction cosine matrix for a planar rotation about the Z axis. If this is the case, your notation is rather confusing, and there is a sign error in one of the terms. Your solution

 y = [x1 x2 -x3; y1 y2 y3; x3 y3 z3]

gives the following matrix:

 cos(v)  sin(v)  0
 sin(v)  cos(v)  0
  0      0       1

Note that you have put a minus sign on a term x3, which is zero. If you desire to construct a direction cosine matrix for a z-axis rotation, one of the sin(v) terms should be negated (depending on the direction of the rotation)

It would be much more clear (and concise) to build your function something like the following;

 sinv=sin(v);
 cosv=cos(v);
 y = [cosv  -sinv 0;  sinv  cosv 0;  0 0 1];