For loop pass in unique rows to function

I have an array that is an X:4 double.

Column 1 of this array is the unique identifier labeled starting at 1 to n.

Example

[1,2.5,3,5 ; 1,3,4,5 ; 1,5,7,5 ; 2,4,5,6 ; 2,6,8,9]

I have a function that takes input normally as 3 columns (X,Y,Z).

I want to write a loop that takes the unique values of column 1 and pushes the rows unique(i:end of i, 2:4) for each unique i in the array that is the X:4

So from the above example it would first push rows 1:3,columns 2:4 to the function and then repeat the for loop to rows 4:5, columns 2:4 to the function.

Answer 1

[Stephen23]

M = [1,2.5,3,5;1,3,4,5;1,5,7,5;2,4,5,6;2,6,8,9];
U = unique(M(:,1));
for k = 1:numel(U)
    X = U(k)==M(:,1);
    yourFunction(M(X,2:4))
end

[Bewler]

Stephen, another beginner question related to this.

The output of the yourFunction is an XYZ array. Is there a way I could set the output of yourFunction(M(X,2:4)) combined with the k value? I want to create a new array from yourFunction that holds the k index in column 1 and the XYZ output of yourFunction to columns 2:4

I'm trying A = A(k,1) + yourFunction but I know it needs to somehow link A(k,1) + A(rows of yourFunction, 2:4).

Output [k,x,y,z,; k,x,y,z,; k,x,y,z,; k,x,y,z,;...]

Maybe I need to do

temporaryarray for the output of yourfunction,

then a [szrow] = size(temporaryarray),

then generate finalarray = finalarray concatenate vertically with finalarray(szrow,1) + concatenate horizontally with finalarray(temporaryarray,2:4)?

I'm just having a difficult time figuring out how to compartmentalize these steps to generate the new array.

[Stephen23]

Here is one solution based around a cell array C that holds the output of each iteration, that should work for output matrices with three columns:

U = unique(M(:,1));
N = numel(U);
C = cell(1,N);
for k = 1:N
    X = U(k)==M(:,1);
    C{k} = yourFunction(M(X,2:4));
    C{k}(:,4) = k;
end
A = vertcat(C{:});
A = A(:,[4,1:3]);

Note that you should not grow arrays inside a loop:

https://www.mathworks.com/help/matlab/matlab_prog/preallocating-arrays.html