choose and change data partially

Hi, i'm beginner on MATLAB.

I take a sinelike data 0 to 2pi.

I want to change some of values and make monotonic increase data.

For example,

• when theta is 0 to pi/2, data is keeping,
• theta is pi/2 to 3pi/2, change values 90-original data,
• theta is 3pi/2 to 2pi, change values 180+original data.

maximum value of original data is 45 at theta pi/2, and minimum value of it is -45 at theta 3pi/2

All of method is ok. thanks to read it.

[FirefoxMetzger]

is your data given by a discrete array / vector of values or via a continous (analytic) function?

Answer 1

[Thorsten]

theta = linspace(0, 2*pi);

idx1 = theta >= pi/2 & theta <= 3*pi/2;
idx2 = theta >= 3*pi/2 & theta <= 2*pi; 

theta(idx1) = 90 - theta(idx1);
theta(idx2) = 180 + theta(idx2);