# How to scatteredInterpolant bwtween data sets?

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Sara am 27 Jan. 2022
Beantwortet: Kartik Saxena am 29 Nov. 2023
Hi,
I have two data sets, x1,y1,z1 (represnting a coordnates as xyz coordnates), and other data set v1, v2,v3 (reprenting a vector field).
I want to interplote the vector fileds into the x1 y1 z1 for each direction.
One of the suggestions is using scatteredInterpolant function.
V = ([v1 v2 v3]);
Fx = scatteredInterpolant(x1,V,'natural','nearest');
Fy = scatteredInterpolant(y1,V,'natural','nearest');
Fz = scatteredInterpolant(z1,V,'natural','nearest');
The problem is the hthe size of v1 v2 v3 are NOT the same size of x1 y1 z1;
Is there any way to overcome this issue?
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### Antworten (1)

Kartik Saxena am 29 Nov. 2023
Hi,
The `scatteredInterpolant` function in MATLAB is used to interpolate scattered data, which means that the points do not need to form a regular grid. However, the vectors representing the coordinates (`x1`, `y1`, `z1`) and the vector field (`v1`, `v2`, `v3`) must have the same length because each entry in the vector field corresponds to a point in the coordinate space.
If the lengths of `x1`, `y1`, `z1` and `v1`, `v2`, `v3` are not the same, you cannot directly create a `scatteredInterpolant` because the function won't know which vector to associate with which point. You need to ensure that each coordinate `(x1(i), y1(i), z1(i))` has a corresponding vector `(v1(i), v2(i), v3(i))`.
Here's how you can approach this problem:
1. Ensure that `x1`, `y1`, `z1` are all column vectors of the same length, and that `v1`, `v2`, `v3` are also column vectors of the same length. Each `i`-th entry in these vectors should correspond to a single data point and its associated vector.
2. Use `scatteredInterpolant` to create interpolants for each component of the vector field separately. The interpolants will map the `(x, y, z)` coordinates to the respective components `(v1, v2, v3)` of the vector field.
Here's an example of how to do this correctly:
% Assuming x1, y1, z1, v1, v2, v3 are all column vectors of the same length
% representing the coordinates and the vector field, respectively.
% Create interpolants for each component of the vector field
Fx = scatteredInterpolant(x1, y1, z1, v1, 'natural', 'nearest');
Fy = scatteredInterpolant(x1, y1, z1, v2, 'natural', 'nearest');
Fz = scatteredInterpolant(x1, y1, z1, v3, 'natural', 'nearest');
% Now you can use Fx, Fy, Fz to interpolate the vector field at any point (x, y, z)
% For example, to interpolate at a new point (x_new, y_new, z_new):
v1_new = Fx(x_new, y_new, z_new);
v2_new = Fy(x_new, y_new, z_new);
v3_new = Fz(x_new, y_new, z_new);
% The interpolated vector at the new point is (v1_new, v2_new, v3_new)
If the lengths of `x1`, `y1`, `z1` and `v1`, `v2`, `v3` are not the same, you need to address this issue before creating the interpolants. You must either:
• Find or generate the missing data so that each coordinate has an associated vector.
• If the data sets are unrelated, you need to reconsider how you are trying to interpolate the vector field and ensure that the data is consistent.
If you have two separate sets of points—one set for the coordinates and one set for the vector field—and you want to interpolate the vector field onto the coordinate points, ensure that `x1`, `y1`, `z1` form one set of points, and `v1`, `v2`, `v3` form another set with the same number of points.
I hope this resolves your issue.
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