Boundary and smooth the figure

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Abdulkarim Almukdad 2021-3-1

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https://ww2.mathworks.cn/matlabcentral/answers/759204-boundary-and-smooth-the-figure

评论： Abdulkarim Almukdad 2021-3-4

I have a very larg data (X, Y, Z) and I used some codes to read the data then remove the columns that contain NaN. The below codes are used after the previous description to plot a 2D graph or 3D with Z being indicated by colors. I tried pcolor and surf but I'm getting the same two problems; 1- the figure is supposed to be perfect x-shape with an angle of 30, but in the middle some portions are connected together which is incorrect. 2- I'm looking for a way to smooth the figure in which the portions where high value of Z be distributed somehow on the adjacent points so that it can be very clear that at this location we have high value of Z (i.e., in my plots this high Z value is showing as a point). I hope that someone can help me doing this. Thanks in advance

x0 = min(x) ; x1 = max(x) ; 
y0 = min(y) ; y1 = max(y) ; 
xi = linspace(x0,x1,150) ; 
yi = linspace(y0,y1,150) ; 
[X,Y] = meshgrid(xi,yi) ;
Z = griddata(x,y,z,X,Y) ;
% Get boundary coordinates 
idx = boundary(x,y) ; 
xb = x(idx) ; yb = y(idx) ; 
% Get points lying inside the boundary 
idx = inpolygon(X,Y,xb,yb) ;
Z(~idx) = NaN ;
f=pcolor(X,Y,Z);
colorbar
shading interp 
axis('equal')

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Mathieu NOE 2021-3-4

在 MATLAB Online 中打开

I was not 100 % successful this time

I increased the "shrink" factor (in the boundary function) so that the triangular areas are reduced but they did not completely vanished

I tried a couple of other approaches but without much benefit

I believe I have to find a robust way to introduce a couple of more points to create the missing corner of the boundary

clc
close all
clear all
num = readtable("01)30.xlsx") ; 
 
% Take all the data under each variable name
x=num{1:1:end, contains(num.Properties.VariableNames, 'x')};
y=num{1:1:end, contains(num.Properties.VariableNames, 'y')};
z=num{1:1:end, contains(num.Properties.VariableNames, 'v')};
% Convert the matrix to 1 column only (scalar)
x=x(:);
y=y(:);
z=z(:);
% Delete rows that contain NaNs with reference to the variable z
i=1; [m,n]=size(x); 
    while i<=m
        
        if isnan(z(i,1))
        x(i,:)=[];
        y(i,:)=[];
        z(i,:)=[];
        i=i-1;      
        end
        i=i+1; [m,n]=size(x);  
        
    end
    
x0 = min(x) ; x1 = max(x) ; 
y0 = min(y) ; y1 = max(y) ; 
xi = linspace(x0,x1,150) ; 
yi = linspace(y0,y1,150) ; 
[X,Y] = meshgrid(xi,yi) ;
Z = griddata(x,y,z,X,Y) ;
% Get boundary coordinates 
idx = boundary(x,y,1) ; 
xb = x(idx) ; yb = y(idx) ; 
a = 0.5;
nd = [a a]/2;
dd = [1 -1+a];
xxb = filtfilt(nd,dd,xb);
yyb = filtfilt(nd,dd,yb);
figure(1),
plot(xb,yb,'*-b',xxb,yyb,'r');
% Get points lying inside the boundary 
% idx = inpolygon(X,Y,xb,yb) ;
idx = inpolygon(X,Y,xxb,yyb) ;
Z(~idx) = NaN ;
figure(2),
f=pcolor(X,Y,Z);
colorbar
shading interp 
axis('equal')

Abdulkarim Almukdad 2021-3-4

Thank you very much for your help. I think I have an idea that might solve this issue but I have zero knowledge about how to do it on matlab unfortunately. I think if the data of each side of the x is ploted and found its boundary, then the combination of both boundaries can do the job. I will try to separate the sides from excel manually by checking each column from simple plottings then I will check what will happen in matlab.

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