MATLAB: In which quadrant is a point

point allocationquadrant

I have a 'circle' with irregular perimeter. Somewhere within that circle is a point. The circle is divided into 4 quadrants by 2 lines 45 and 135 degrees to x- axis.I know the coordinates of the point. How can I find exactly in which quadrant it lies?

Thank you

Best Answer

The four quadrants are characterized by the following conditions (if the center of the circle is at (0,0)):

I quadrant: y<=x, y>=-x
II quadrant: y>=x y>=-x 
III quadrant: y<=x, y>=-x 
IV quadrant: y<=x, y<=-x

Use an if-statement to determine which quadrant the point under consideration is in.

Best wishes

Torsten.

Related Solutions

MATLAB: Counting using Statistics tools

Presumably you already have the (x,y) coordinates if you've plotted the data.

You just need to use indexing (the main superpower of Matlab) to determine which points are in which quadrants.

For example,

centerPoint_x = min(xlim) + range(xlim)/2; 
centerPoint_y = % Same thing as above but with ylim
quad1 = x >= centerPoint_x & y >= centerPoint_y; 
quad2 = x < centerPOint_x & y >= centerPoint_y; 
quad3 = % fill in....
quad4 = % file in....
% Points that are in Quad1 are 
x(quad1), y(quad1)

MATLAB: Making of a movie, rotating a circle at an input distance from centre.

I managed to solve it myself, here's the final code.

%-------------------------------

function rotateCircle(a,rotRad)

close all

circleRadius = sqrt(a/pi);

cx = 0;

cy = 0;

for j = 1:30

    cx = rotRad*cos(j*2*pi/30);
    cy = rotRad*sin(j*2*pi/30);
    drawDisk(cx,cy,circleRadius);
    mov(j) = getframe;
end
movie(mov,11,24);
end
%-------------------------------

function drawDisk(cx,cy,radius)
[x,y] = meshgrid(-200:200);
circleImage = (x-cx).^2 + (y-cy).^2 < radius^2; % the disk
imagesc(x(:,1),y(:,1),circleImage);
%-------------------------------

Best Answer

Related Solutions

MATLAB: Counting using Statistics tools

MATLAB: Making of a movie, rotating a circle at an input distance from centre.

Related Question