How do I get the x,y coordinates from the scatter graph I generated?

Hi, I need to get those values to put into an equation. Can anyone help me? Here is the example code that I wrote. Thanks.

xrange = 0:100;
yrange = 0:100;
a= randi(numel(xrange),15,1); %randomly choose xcoordinate
b = randi(numel(yrange),15,1); %randomly choose ycoordinate
scatter(a(:),b(:),2000,'r')
for k=1:numel(a,b)
      text(a(k),b(k),['(' num2str(a(k)) ',' num2str(b(k)) ')'])
end

Answer 1

[Zoltán Csáti]

You created the scatter plot in view of vectors a and b. So those are the coordinates. Supposing you only have the scatter plot and you want to extract the coordinates:

   sc = findobj(gca,'Type','hggroup');
   xCoord = get(sc, 'XData');
   yCoord = get(sc, 'YData');

[ker fang fang]

how do i change the variable? i need those coordinate in the graph to be put into an equation, say, f(x,y)= x+y^2.

[Zoltán Csáti]

When you have the vectors xCoord and yCoord, you put into function f as follows:

f = xCoord + yCoord.^2;

[ker fang fang]

but my program in terms of a,b. so how do i change it? is it like that?

sc = findobj(gca,'Type','hggroup');
a = get(sc, 'XData');
b = get(sc, 'YData');
f = a + b.^2;

[Zoltán Csáti]

Yes.

[ker fang fang]

but there is no response or any answer by that equation, it seem like the program after the for loop, does not read it. how to solve it?

the code

if true
  % code
xrange = 0:100;
yrange = 0:100;
a= randi(numel(xrange),15,1); %randomly choose xcoordinate
b = randi(numel(yrange),15,1); %randomly choose ycoordinate
scatter(a(:),b(:),2000,'r')
for k=1:numel(a,b)
    text(a(k),b(k),['(' num2str(a(k)) ',' num2str(b(k)) ')'])
end
sc = findobj(gca,'Type','hggroup');
a = get(sc, 'XData');
b = get(sc, 'YData');
f = a + b.^2;

[Zoltán Csáti]

I do not really know what you want. You have vectors a and b at disposal.

Answer 2

[Image Analyst]

The answer to your question is that you already have "a" and "b" so you have the "x,y coordinates" that you're requesting. Like Zoltan already told you, there is no need to call get() to extract it from the plot when it was YOU who created the plot - you must have the coordinates to create the plot in the first place.

If you want some kind of interpolated surface for every value of a and b, even those where you don't have any training data, try scatteredInterpolant().