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

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.

Answer 1

[KSSV]

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) ;