Generating empty interval of points

Dear All,

I want to generate points in the interval [20,80] and have the interval [40,60] as an empty area. I wrote this code but I don't now how to complete it. I'd appreciate any help.

LB=20;UB=80;
x = LB+(UB-LB)*rand(50,1);
y =LB+(UB-LB)*rand(50,1);
if x>40 | x<60| y>40 | y<60;
  [x]==0;[y]==0;  
  plot(x,y, '.')

but it gives an error.

Regards

Answer 1

[Star Strider]

This seems to work:

LB=20;UB=80;
x = LB+(UB-LB)*rand(50,1);
y = LB+(UB-LB)*rand(50,1);

idx = [((x > 40) & (x < 60)) | ((y > 40) & (y < 60))];
x(idx) = [];
y(idx) = [];

figure(1)
plot(x, y, '+')
grid

The ‘idx’ variable tests for the conditions and creates a logical vector then used to assign the elements of ‘x’ and ‘y’ to ‘empty’ rather than zero. The plot shows that there are no points in the area you want cleared.

[imola]

Dear Star,

Thanks for you and for Roger for answer me, I realize that I didn't explain what I want exactly, forgave me both of you, with your code I got four areas of points separate of each other while I need a whole area of points and an empty area in the middle, is like an empty square inside a big square of points, so I tried to use

t = ((x<=40)||(x>=60)) && ((y<=40)||(y>=60));

but its wrong, could you please sorted to me.

Regards,

Imola.

[Star Strider]

@imola — Change only the ‘idx’ line in my code to:

idx = [((x > 40) & (x < 60)) & ((y > 40) & (y < 60))];

to get this plot:

[Image Analyst]

That does give an empty square in the 40-60 range. It relies on tossing out points that initially landed in there, so that the final number of points is most likely less than 50. Do you need exactly 50 points in there, or is it okay to get however many you end up with?

[imola]

Thanks Star, that's fine, it works perfectly .

Regards

[Star Strider]

My pleasure!

Answer 2

[Roger Stafford]

Do this:

   LB=20;UB=80;
   x = LB+(UB-LB)*rand(50,1);
   y = LB+(UB-LB)*rand(50,1);
   t = ((x<=40)|(x>=60)) & ((y<=40)|(y>=60));
   x = x(t);
   y = y(t);
   plot(x,y,'.')

[imola]

Dear Roger, Thanks for you and for star for answer me, I realize that I didn't explain what I want exactly, forgave me both of you, with your code I got four areas of points separate of each other while I need a whole area of points and an empty area in the middle, is like an empty square inside a big square of points, so I tried to use

t = ((x<=40)||(x>=60)) && ((y<=40)||(y>=60));

but its wrong, could you please sorted to me.

Regards,

Imola.