Data picking from grid
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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.
采纳的回答
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
11 个评论
aa
2020-9-12
KSSV
2020-9-12
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
2020-9-12
KSSV
2020-9-12
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
2020-9-12
KSSV
2020-9-12
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
2020-9-12
I just apply your code and get this 
KSSV
2020-9-12
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
2020-9-12
KSSV
2020-9-12
Edited the answer.
aa
2020-9-12
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