# Decimal indexing for arrays in MATLAB

15 vues (au cours des 30 derniers jours)
If I have a array of 11 elements, within the range 1 and 2, with a difference of 0.1, i.e, m = 1:0.1:2; to access the value of '1.4000' from the array 'm', the normal procedure is to write 'm(5)'. (index must be an integer)
Can I somehow index 'm(1.4)' and get the value 1.4000? (have a decimal value in the index)
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Bjorn Gustavsson le 10 Jan 2023
Sometimes I see 1-D interpolation that way - this require the array to have some simple interpretation of samples of a sufficiently smooth function that the samples in the array can be used to build useful estimates for your "fractional" indices. But indexing is to elements you have.
Modifié(e) : Yuvarajendra Anjaneya Reddy le 10 Jan 2023
@DGM Sorry for not being descriptive of my issue. I have a mesh grid [X,Y] = ndgrid (1:256, 1:256); and another matrix u = sin(X) + cos (Y); I have interpolated 10 values between every consequtive values in all the matrices.
If I need to access the value 'u' when X = 1.4, and Y = 2.8, i.e, u_interp(1.4, 2.8), then I have trouble, as I will have to create new Indices or run the interp2 command again to access the values. So, I thought decimal indexing would be a way..
[X,Y] = ndgrid (1:256, 1:256);
u = sin(X) + cos (Y);
%Interpolation
[Xq, Yq] = ndgrid(1:(1/10):256, 1:(1/10):256);
F = griddedInterpolant(X, Y, u, 'spline');
u_interp = F(Xq, Yq);

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### Réponse acceptée

Bjorn Gustavsson le 10 Jan 2023
Have a look at the help and documentation for griddedInterpolant. That function might be what you're looking for. It creates a function that interpolates over a gridded data. For repeated calls this means that it has kept the structure for interpolation such that you won't redo all the set-up you'd do with repeated calls to interp2 again and again with repeated calls.
HTH
##### 1 commentaireAfficher -1 commentaires plus anciensMasquer -1 commentaires plus anciens
@Bjorn Gustavsson Thank you for pointing me to the solution. This is what I was looking for.

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