Algorithm (Workflow)

This function, rcofind, is designed to convert a list of linear indices into a list of row and column indices for a matrix. It is particularly useful when working with 2D matrices in MATLAB, where you need to convert a scalar index into its corresponding row and column indices.

Input Parameters

• s: A vector representing the size of the matrix. It is expected to be in the form [rows, cols].
• il: A list of linear indices that need to be converted into row and column indices.

Output

• RCL: A matrix where each row corresponds to a pair of row and column indices derived from the input index list.

Algorithm Steps

1. Check if the input index list il is a row vector. If not, transpose it to ensure it is a row vector.
2. Verify that all indices in il are within the valid range of the matrix size specified by s. If any index exceeds the maximum possible index (i.e., s(1) * s(2)), an error is thrown.
3. Calculate the row indices using the mod1 function, which adjusts the indices to fit within the number of rows specified by s(1).
4. Calculate the column indices by dividing each index in il by the number of rows s(1) and taking the ceiling of the result.
5. Combine the row and column indices into a matrix RCL, where each row contains a pair of row and column indices.

Example Usage

Consider a 5x5 matrix M with some NaN values. The function rcofind can be used to find the row and column indices of these NaN values:

m = 5;
M = circshift(reshape(1:m*m, m, []), [floor(randminv(m)), floor(randminv(m))]);
n = m;
for i = 1:n
    M(floor(randminv(m)), floor(randminv(m))) = nan;
end
l = find(isnan(M));
rcofind(size(M), l);
rcofind(size(M), l');

This example demonstrates how to use the function to convert the linear indices of NaN values into their corresponding row and column indices.