Interpolating contour plot using user input
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Hello,
I have created a 2D contour map using a 25x19 matrix and was wondering how to interpolate the value at certain user-input x-y coordinates? Essentially, I want the user to enter coordinates that are either integer or decimal, and for the code to output the value at that corresponding location. Any help would be appreciated :)
data = readmatrix('pixeltxt.txt');
contourf(data);
grid minor
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Bram Schroeders
2021-1-20
0 个投票
I think taking a look at this documentation may help you https://www.mathworks.com/help/matlab/ref/scatteredinterpolant.html
13 个评论
Radhika Kulkarni
2021-1-20
Radhika Kulkarni
2021-1-21
Is it possible to convert my 25x19 matrix using Matlab code (picture attached) to fit a function in terms of z = f(x,y)? That way, I can enter x and y coordinates and the output will be the cooresponding value at that location.
Bram Schroeders
2021-1-21
编辑：Bram Schroeders
2021-1-21
This is exactly what the scatteredinterpolant function does for you. x and y would in this case be the indices of the values in the matrix. To create a vector to input in the function you can use a for loop like this:
A = rand(25,19) %In your case this would be your matrix and not 'rand(25,19)'
x = [];
y = [];
v = [];
for i = 1:size(A,1)
for j = 1:size(A,2)
x = [x; i];
y = [y; j];
v = [v; A(i,j)]
end
end
Now you can create the interpolant function like this:
f = scatteredInterpolant(x,y,v)
and you can read the values like this:
xi = % The x value you want to interpolate at
yi = % The y-value you want to interpolate at
I = f(xi,yi) % The interpolated value
Radhika Kulkarni
2021-1-21
Bram Schroeders
2021-1-21
编辑：Bram Schroeders
2021-1-21
Oh, i see i made a typo. The for loop should be like this:
for i = 1:size(A,1)
for j = 1:size(A,2)
x = [x; i];
y = [y; j];
v = [v; A(i,j)]
end
end
I also corrected my previous comment
Radhika Kulkarni
2021-1-21
编辑：Radhika Kulkarni
2021-1-21
Radhika Kulkarni
2021-1-25
编辑：Radhika Kulkarni
2021-1-25
Bram Schroeders
2021-1-26
use:
grid on;
xlim([-21.4 -19.6]);
ylim([-17.5 -15]);
Radhika Kulkarni
2021-1-26
It returned this:
Bram Schroeders
2021-1-26
This is exactly what i would expect that it returns. If this is not what you want, i don't understand your question.
Radhika Kulkarni
2021-1-26
Bram Schroeders
2021-1-26
You can use the rescale function:
So for instance you have a vector called A and you want to set the x-axis to [-21.4 -19.6] and y-axis to [-17.5 -15] you can do this:
A(:,1) = rescale(A(:,1),-21.4,-19.6);
A(:,2) = rescale(A(:,2),-17.5,-15.0);
I think this is what you mean
piston_pim_offset
2023-11-18
Thanks for your answers Bram Schroeders
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