Data picking from grid

I have data in three column (x,y,z)

I want to pick the values of z in each grid ...

For exmaple, in fiure, the values of x are plotted coressponding to x,y. Then with a diffrenec of 1 we grided the plot.

I want to calculate the data points placed in each grid.

Answer 1

[KSSV]

I have edited the code for your given points so that you can get the points for each grid.

x = -130.7:0.1:-129.7 ; 
y = 45.6:0.1:46.3 ;
n = length(x) ;
m = length(y) ; 
[X,Y] = meshgrid(x,y) ; 
data = importdata("data.txt") ; 
x = data(:,1) ; y = data(:,2) ; z = data(:,3) ;
% plot grid 
plot(X,Y,'r',X',Y','r')
hold on 
for i = 1:m-1
  for j = 1:n-1
    % Get the points of each grid 
    P = [X(i,j) Y(i,j) ; 
         X(i,j+1) Y(i,j+1) ; 
         X(i+1,j+1) Y(i+1,j+1) ;
         X(i+1,j) Y(i+1,j)] ; 
         
    idx = inpolygon(x,y,P(:,1),P(:,2)) ; 
    iwant = [x(idx) y(idx) z(idx)] ; 
    plot(x(idx),y(idx),'.')
    drawnow
   end
end

[aa]

Thank you very much . We are very close to the required result. But, I want to place a third parameter in x-y grid. How can i do so ...

[KSSV]

You need not to worry about the third parameter, you can use the indices obtained to print the third parameter. I have edited the answer to include the third parameter.

[aa]

Thank you let me try this in my data set. In the next phase, I want to get an output as the point in each grid point.

[KSSV]

You can also use inequalities to get the points lying inside the grid if you are not okay with inpolygon.

m = 4;
n = 4 ;
x = linspace(0,1,m) ;
y = linspace(0,1,n) ; 
[X,Y] = meshgrid(x,y) ;
% Pick some random points 
x = rand(100,1) ;
y = rand(100,1) ;
z = rand(100,1) ; 
% Get points lying inside the grid/ square
P = [0 0 ;0.3333 0 ; 0.3333 0.3333 ;0. 0.3333] ;
idx = inpolygon(x,y,P(:,1),P(:,2)) ; 
iwant = [x(idx) y(idx) z(idx)] ; 
% Use ineqialities 
idx1 = x >= min(P(:,1)) & x <= max(P(:,1)) ; 
idy1 = y >= min(P(:,2)) & y <= max(P(:,2)) ; 
idxy = idx1 & idy1 ; 
% plot grid 
plot(X,Y,'r',X',Y','r')
hold on
plot(x,y,'ok')
plot(x(idxy),y(idxy),'+b')

[aa]

Thanks let me share with you the data set that i want to process ...

The grid dimensions are

x = linspace(-130.7,0.1,-129.7 ) ;

y = linspace(45.6,0.1,46.3) ;

Now we have to place the coresspodning enteries of z in the grid of x-y.

One the values placed in each grid after that i have to apply further analysis for teh enteries of each grid point

[KSSV]

x = -130.7:0.1:-129.7 ; 
y = 45.6:0.1:46.3 ;
[X,Y] = meshgrid(x,y) ; 

And you can proceed as given in the answer above.

[aa]

I just apply your code and get this

[KSSV]

Do you think the points given in P i.e polygon/ rectangle form a closed region? The code is correct it should work if you give all the details correct.

[aa]

Yes, the code is working perfectly, but one last thing is the calculation of "iwant" for each grid point. In case of manual calculation, I change the points of p for each grid.

[KSSV]

Edited the answer.

[aa]

Thank you this is really amazing and work perfectly, But if i want to get an output file of data points in each grid , how can this be possible.