Interpolation of matrix with data that is of different dimensions

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James Rodriguez 2021-3-13

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https://ww2.mathworks.cn/matlabcentral/answers/771433-interpolation-of-matrix-with-data-that-is-of-different-dimensions

评论： Walter Roberson 2021-3-13

The code below attempts to interpolate from a matrix (13x10) which contains velocities corresponding to some x points(1x10) and y points (13x1). I need to find the velocity for the same 10 x points but with different y points (10x1). I have tried the following to interpolate the matrix, however, I can't get a code that runs. Am I using the correct technique? If so why isn't this working? And if not then I am grateful for any assistance.

x_points = [3,6,9,12,15,18,21,24,27,30]; % X values for the function 
y_points = [1,2,3,4,5,6,7,8,9,10,11,12,13]; % Y values for the function 
Yq = [12.7,11.16,11.68,10.99,12.98,3.61,9.291,0.18,9.86,3.64] % The points for which I need the function value 
Xq = x_points
F = interp2(x_points,y_points,V1,x_points,interpolate_me); % Output the matrix withe the data 

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Answer 1

Walter Roberson 2021-3-13

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https://ww2.mathworks.cn/matlabcentral/answers/771433-interpolation-of-matrix-with-data-that-is-of-different-dimensions#answer_646713

编辑：Walter Roberson 2021-3-13

在 MATLAB Online 中打开

V1 = sort(randi(9,13,10));
x_points = [3,6,9,12,15,18,21,24,27,30]; % X values for the function 
y_points = [1,2,3,4,5,6,7,8,9,10,11,12,13]; % Y values for the function 
Yq = [12.7,11.16,11.68,10.99,12.98,3.61,9.291,0.18,9.86,3.64] % The points for which I need the function value 
Yq = 1×10
   12.7000   11.1600   11.6800   10.9900   12.9800    3.6100    9.2910    0.1800    9.8600    3.6400
Xq = x_points
Xq = 1×10
     3     6     9    12    15    18    21    24    27    30
F = interp2(x_points,y_points,V1, Xq, Yq); % Output the matrix withe the data 
F
F = 1×10
    8.7000    7.1600    9.0000    8.0000    8.9800    2.6100    5.5820       NaN    5.8600    3.0000

The Nan is because the Y query 0.18 is before any define y coordinate.

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James Rodriguez 2021-3-13

Thank you so much! Works perfectly. If I wanted to run this for multiple functions (v1.v2...) , is there an efficent way of doing this? I tried to form one matrix with all the function matrices and run that but it will not give an ouput .

Walter Roberson 2021-3-13

Not really. There is a temptation to say "use interp3" with the third coordinate being the function number, but the problem with that is that it will mix between functions. Though maybe if you used a third coordinate that was on a much larger scale then the mixing would be minimal.

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