def extract_line(matrix, point, xyincrement):
    """ Takes an x by x matrix and scans a matrix for a list of items.

        Uses a starting point tuple (x, y) and an increment tuple(x-increment, y-increment).
        Starts the list from the x, y coordinate and goes in the increments given by xinc and yinc.
    """
    x, y = point[0], point[1]
    xinc, yinc = xyincrement[0], xyincrement[1]
    items = []

    while x >= 0 and y >= 0 \
            and x < len(matrix) and y < len(matrix):
        items.append(matrix[y][x])
        x += xinc
        y += yinc
    return items