How can I interpolate with a Matrix and a Vector to another vector?

Question

José Cabrera 2019-8-20

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https://ww2.mathworks.cn/matlabcentral/answers/476779-how-can-i-interpolate-with-a-matrix-and-a-vector-to-another-vector

回答： KSSV 2019-8-20

采纳的回答： KSSV

在 MATLAB Online 中打开

Hi there,

I have the following data in MATLAB, as two vectors (Temperature and Concentration) and one matrix (Enthalpy):

I use the following code to get a value within the Enthalpy matrix using both vectors:

interp2(Temperature,Concentration,Enthalpy,10,5)
ans = 37,22

Thats ok; Now I would like to get a value within Temperature Vector using the Concentration Vector and the Enthalpy Matrix as:

interp2(Concentration,Enthalpy,Temperature,55.58,88.6199)

which should give a value between 30°C and 40°C, but I get:

Error using griddedInterpolant
The number of input coordinate arrays does not equal the number of dimensions (NDIMS) of these arrays.
Error in interp2>makegriddedinterp (line 228)
    F = griddedInterpolant(varargin{:});
Error in interp2 (line 136)
        F = makegriddedinterp(X, Y, V, method,extrap);

Im little new using MATLAB, it surely shall be a dimension problem when I trying interpolate using a matrix and vector.

If anyone has any idea how to this, any help would be greatly appreciated.

Kind regards,

José C.

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Answer 1

KSSV 2019-8-20

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/476779-how-can-i-interpolate-with-a-matrix-and-a-vector-to-another-vector#answer_388265

在 MATLAB Online 中打开

YOu see, you cannot use Enthalpy as you have used, because it is not a valid meshgrid. Reather, you can treat the data as scattered data and use to get the values you want. Check the below demo code.

[X,Y,Z] = peaks(100) ; 
val1 = interp2(X,Y,Z,3,3) ;   % this works; X, Y are valid meshgrid 
% val2 = interp2(X,Z,Y,3,val1) ; % this doesnot work; Z is not a avalid grid 
F = scatteredInterpolant(X(:),Z(:),Y(:)) ; 
val2 = F(3,val1) ;