如何修改Matlab查找表函数，改用主对角线与反对角线计算？

Got it, let's tweak your existing lookup function to use Y1's main diagonal and Y2's anti-diagonal instead of fixed rows/columns. Here's the revised code and breakdown:

Revised Function Code #

function [x1,x2] = lookup_tab(y1,y2,X1,X2,Y1,Y2)
    % Extract main diagonal elements from Y1
    y1_main_diag = diag(Y1);
    % Find index of element closest to y1 (min absolute difference)
    [~, m] = min(abs(y1_main_diag - y1));
    
    % Extract anti-diagonal elements from Y2: flip columns first, then take main diagonal
    y2_anti_diag = diag(flip(Y2, 2));
    % Find index of element closest to y2 (min absolute difference)
    [~, n] = min(abs(y2_anti_diag - y2));
    
    % Retrieve scalar values from X1 and X2 using the calculated indices
    x1 = X1(n,m);
    x2 = X2(n,m);
end

Key Changes Explained #

Let's walk through how this differs from your original code:

• Replacing fixed row/column with diagonals:

  • For Y1: Instead of targeting a specific row with Y1(row,:), we use diag(Y1) to grab all elements where the row index equals the column index (the main diagonal).
  • For Y2: To get the anti-diagonal (elements where row index + column index = matrix size + 1), we first flip Y2 horizontally with flip(Y2, 2), then extract the main diagonal of the flipped matrix—this gives us the original Y2's anti-diagonal elements.

• Index compatibility:

  • The index m returned by min() for Y1's diagonal directly maps to the column (and row) index of the closest element in Y1, matching how m was used as a column index in your original code.
  • The index n returned for Y2's anti-diagonal maps to the row index of the closest element in the original Y2 matrix, just like n was used as a row index originally.

• Handling non-square matrices (optional):
  If Y1 or Y2 aren't square, diag() will extract the longest possible diagonal starting from the top-left corner. If you need to explicitly handle non-square cases for the anti-diagonal, you can replace the anti-diagonal extraction line with this more explicit version:

  % Get indices for Y2's anti-diagonal (works for non-square matrices)
  diag_length = min(size(Y2));
  row_indices = 1:diag_length;
  col_indices = size(Y2,2):-1:size(Y2,2)-diag_length+1;
  y2_anti_diag = Y2(sub2ind(size(Y2), row_indices, col_indices));
  

内容的提问来源于stack exchange，提问作者Shika93