How to plot a mashgrid within an ir-regular shape?

Hi everyone,

I am looking to plot a meshgrid figure with an irregualr shape and then need to need the grids within a bounded regions along with the central location of each grid point.

Here is what i did so far:

% Step 1: Create a rectangualr meshgrid considering the region of
% ir-regualr bounded area 

clear all
clc

x=72.68:0.005:72.97;
y=34:0.005:34.7;
n = length(x ) ;
m = length(y ) ;
[X,Y] = meshgrid(x,y ) ;
plot(X,Y,'r',X',Y','r ')
%Result is as below

Step 2: Plot dimensions of the bounded area over the meshgrid map

clear all
clc

x=72.68:0.005:72.97;
y=34:0.005:34.7;
n = length(x ) ;
m = length(y ) ;
[X,Y] = meshgrid(x,y ) ;
plot(X,Y,'r',X',Y','r ')
hold on

data=readmatrix('dam_area.csv');
x1=data(:,1);
y1=data(:,2);
z1=data(:,3)*0;
plot(x1, y1, 'blue')

%Result as below

What I need at the first stage?

I want to delete all the grid outside the bounded area and only keep the griids inside the bounded area.

expected results as below (@KSSV help in plotting this, but not very sure about the approach)

What else I need?

I require to know the central value (lat, long values, assume z here zero) of each grid (with the bounded area) so i can use thouse central values to plot other parameteres with the same grids.

Thank you!

(Data is attached).

[KSSV]

Share your csv file.....

[Andi]

@KSSV Apology, I have already uploaded the csv file.

Answer 1

[KSSV]

clc; clear ;
x=72.68:0.005:72.97;
y=34:0.005:34.7;

n = length(x ) ;
m = length(y ) ;
[X,Y] = meshgrid(x,y ) ;
data=readmatrix('https://www.mathworks.com/matlabcentral/answers/uploaded_files/1385964/area.csv/area.csv');
x=data(:,1);
y=data(:,2);
z=data(:,3);
F = scatteredInterpolant(x,y,z) ; 

Warning: Duplicate data points have been detected and removed - corresponding values have been averaged.

Z = F(X,Y) ; 
%x = axil_long ; y = axil_lat ; z = time_axil(:,1) ;
[in,on] = inpolygon(X,Y,x,y) ; 
idx = in|on ; 
X(~idx) = NaN ;
Y(~idx) = NaN ;
Z(~idx) = NaN ; 

figure
h = pcolor(X,Y,Z) ;
h.EdgeColor = 'none';

figure
plot(X,Y,'r',X',Y','r ')
xlabel('Longitude (E{\circ})')
ylabel('Latitude (N{\circ})')



axis([72.68  72.97  34  34.7])

[Andi]

@KSSV Thanks this works well, can I get the central location of each grid point of the mesh grid, so I can place other parameters within each grid?

My major task is to find the central points (lat, long) of each grid with the bounded area and then fill each grid cell with other parameters one by one.

[KSSV]

% Central location 
xc = x(1)-0.0025:0.005:x(end)-0.0025;
yc = y(1)-0.0025:0.005:y(end)-0.0025;
[Xc,Yc] = meshgrid(xc,yc) ; 

[Andi]

@KSSV Thanks for help! I think it still only give one point whereas i am looking for centeral point of all the grids within the bounded region.

[KSSV]

Use Xc, Yc as you have used X, Y. Xc, Yc are central points.

[Andi]

@KSSV Thanks, but I think my objective is a bit different. Let me try to explain it a bit clearer.

x=72.68:0.005:72.97;

y=34:0.005:34.7;

Above x, and y are the grid points over the whole area.

data=readmatrix('https://www.mathworks.com/matlabcentral/answers/uploaded_files/1385964/area.csv/area.csv');

x1=data(:,1);

y1=data(:,2);

z1=data(:,3)*0; % assume z=0 here

x1, y1 are marked as the boundary of the enclosed area over the x, y grid. Next, I want to find the grids lying with the x1, y1 area and their central values, so I can use that central values to plot other parameters with each grid point.

I am trying to get through what you explained to me, but still not very clear to me.

May you assist me here? Thank you!

[KSSV]

clc; clear ;
x=72.68:0.005:72.97;
y=34:0.005:34.7;

n = length(x ) ;
m = length(y ) ;
[X,Y] = meshgrid(x,y ) ;
% Central location 
xc = x(1)-0.0025:0.005:x(end)-0.0025;
yc = y(1)-0.0025:0.005:y(end)-0.0025;
[Xc,Yc] = meshgrid(xc,yc) ; 

data=readmatrix('https://www.mathworks.com/matlabcentral/answers/uploaded_files/1385964/area.csv/area.csv');
x=data(:,1);
y=data(:,2);
z=data(:,3);
F = scatteredInterpolant(x,y,z) ; 

Warning: Duplicate data points have been detected and removed - corresponding values have been averaged.

Z = F(X,Y) ; 
%x = axil_long ; y = axil_lat ; z = time_axil(:,1) ;
[in,on] = inpolygon(X,Y,x,y) ; 
idx = in|on ; 
X(~idx) = NaN ;
Y(~idx) = NaN ;
Z(~idx) = NaN ; 

[in,on] = inpolygon(Xc,Yc,x,y) ; 
idx = in|on ; 
Xc(~idx) = NaN ;
Yc(~idx) = NaN ;

figure
hold on
plot(X,Y,'r',X',Y','r ')
plot(Xc,Yc,'.b')

xlabel('Longitude (E{\circ})')
ylabel('Latitude (N{\circ})')



axis([72.68  72.97  34  34.7])

[Andi]

@KSSV Thanks for the updated results, I am trying to test it on the actual data set. Meanwhile, I also updated my primary question for clarity.

[Andi]

@KSSV I attempt to fix the probelm with the gridding approch but it did not work well, so i move to another approch.

Step 1: Plooting the boundary of ir-regular shape

data=readmatrix('dam_area.csv');
x=data(:,1);
y=data(:,2);
z=data(:,3);
plot(x, y, 'blue')
hold on 

Step 2: Plotting the z-parameteres as a color color within the bounded area

dat=readmatrix('combine.csv');
x1=dat(:,2);
y1=dat(:,3);
c1=dat(:,4);
plot(x1, y1, 'blue')
scatter(x1,y1,[],c1,'filled')
colorbar
colormap jet

hold off

What I required:

1. Interpolate all the scatter points and make a surface plot (figure attached below).
2. The mesh grid is this bounded area and gets the central point of each mesh grid along with the average value of the z-parameter.

Thanks