Emacs command to transpose the contents of a (La)TeX table.

LaTeX-transpose-table.el

(defun LaTeX-transpose-table (start end)
  (interactive "r")
  (goto-char start)
  (let ((last start)
        (rows (list ()))
        (nrows 0)
        (ncols 0)
        (maxcols 0))
    (while (re-search-forward "&\\|\\\\\\\\" end t)
      (setf (car rows) 
            (cons (buffer-substring last (match-beginning 0)) (car rows)))
      (incf ncols)
      (when (string= "\\\\" (match-string-no-properties 0))
        (setq maxcols (max maxcols ncols))
        (setq rows (cons () rows))
        (incf nrows)
        (setq ncols 0))
      (setq last (match-end 0))
      (goto-char last))
    ;; empty row
    (setq rows (cdr rows))
    ;; now output the transposed variant
    (kill-region start end)
    (insert 
      (let (i j table trow)
        (loop for j from 1 upto maxcols collect
          (loop for i from 1 upto nrows
            collect (let* ((row (nth (- nrows i) rows)) 
                           (cell (if row (nth (- maxcols j) row) "")))
                      (concat cell (if (< i nrows) "&" "\\\\\n")))
            into trow
            finally return (apply 'concat trow))
          into table
          finally return (apply 'concat table)))))
  (message "Old table saved to kill ring."))

Very nice, simple and flexible. I just downloaded it, tried it, and it worked!

Thank you :)