Interpolation of given data in 2d domain
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x=0,4,6,9,11,17,20
y=0,2,3,7,10,15
x is (7,1) vector & y is (6,1)
z will have (known data) 7*6=42 values in this domain.
how to interpolate z to some new x & y. let say now x(5,1)=0,5,10,15,20 & y(6,1)= 0,3,6,9,12,15.
I am using "griddata" bit getting very lil error. please help!
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回答(1 个)
Davide Masiello
2023-4-5
Example
xdata = linspace(1,10,10)
ydata = linspace(0,1,11)
zdata = rand(length(ydata),length(xdata))
x0 = [2.5 3.5 4.5 5.5];
y0 = [0.25 0.35 0.45 0.55];
z0 = interp2(xdata,ydata,zdata,x0,y0)
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Davide Masiello
2023-4-6
编辑:Davide Masiello
2023-4-6
xdata = linspace(1,10,20);
ydata = linspace(0,20,30);
[xgrid,ygrid] = meshgrid(xdata,ydata);
zdata = sin(xgrid)+cos(ygrid);
figure(1)
surf(xgrid,ygrid,zdata)
Now, if you want data at a certain fixed x0 and variable y, you can do
x0 = 6.5;
z0 = interp2(xdata,ydata,zdata,x0,ydata);
You can visualise this
figure(2)
subplot(2,1,1)
surf(xgrid,ygrid,zdata),hold on
plot3(x0*ones(size(ydata)),ydata,z0,'r','LineWidth',4)
subplot(2,1,2)
plot(ydata,z0)
xlabel('y')
ylabel('z')
legend('x0 = 6.5')
Same thing for fixed y0
y0 = 5.66;
z0 = interp2(xdata,ydata,zdata,xdata,y0);
figure(3)
subplot(2,1,1)
surf(xgrid,ygrid,zdata),hold on
plot3(xdata,y0*ones(size(xdata)),z0,'r','LineWidth',4)
subplot(2,1,2)
plot(xdata,z0)
xlabel('y')
ylabel('z')
legend('y0 = 5.66')
In general, you can extrapolate any path on the surface of z for a given function y(x).
x0 = xdata;
y0 = -2*x0+18;
z0 = interp2(xdata,ydata,zdata,x0,y0);
figure(4)
subplot(2,1,1)
surf(xgrid,ygrid,zdata),hold on
plot3(x0,y0,z0,'r','LineWidth',4)
subplot(2,1,2)
plot3(x0,y0,z0,'k','LineWidth',2)
xlabel('x')
ylabel('y')
zlabel('z')
legend('y = -2x+18')
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