MATLAB: How can I make atan output unlimited

atanMATLAB and Simulink Student Suite

Hi guys, I'm having a bit of a mathematical/programming problem here, I hope u could help me. somewhere in my simulink files when I'm trying to solve a control problem. here goes a simple description. I've got something that is equal to sin(theta) and something that is equal to cos(theta). in other words I have two equations sin(theta)=y and cos(theta)=x. both equations can be solved at the same time by diving that we get tan(theta)=y/x. so when u want to find theta, u'll have; theta=atan(y/x) the only problem is that as I know the system, theta goes from zero to ascending to infinity (if u don't shut it down) but the output of atan function is limited between -pi/2 and pi/2. so what should I do yo let it ascend after pi/2 till pi, 2*pi, 3pi and so on? I need the output to be continuous. thanks in advance.

Best Answer

You need to use the atan2 function. If you want the angles it reports to be continuous from 0 to 2*pi or to 360°, use one of these anonymous functions:

Angles360 = @(a) rem(360+a, 360);                        % For ‘atan2d’
Angles2pi = @(a) rem(2*pi+a, 2*pi);                      % For ‘atan2’

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MATLAB: How to get the wind speed and direction values from u and v components

The ‘u’ and ‘v’ are the ‘x’ and ‘y’ components of the plotted vector. To get the magnitude, use the hypot function, and to get the direction, use the atan2 function. You can use these little utility functions to convert the atan2 or atan2d output to [0,p2*pi] or [0,360] representation:

Angles360 = @(a) rem(360+a, 360);                        % For ‘atan2d’
Angles2pi = @(a) rem(2*pi+a, 2*pi);                      % For ‘atan2’

These results will correspond to the mathematical convention for angle orientation, not the compass convention.

MATLAB: How to define a function that evaluates in input

function y=T(theta_Degree)
theta=theta_Degree*pi/180;
y=[cos(theta)^2 sin(theta)^2 2*cos(theta)*sin(theta);sin(theta)^2 cos(theta)^2 -2*cos(theta)*sin(theta);-cos(theta)*sin(theta) cos(theta)*sin(theta) cos(theta)^2-sin(theta)^2];
end

Then type in command line

T(40)

and see the results.

Best Answer

Related Solutions

MATLAB: How to get the wind speed and direction values from u and v components

MATLAB: How to define a function that evaluates in input

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