xchange transform real to pixel coordinates [x1, y1, rect] = xchange(x, y, dir) x, y two matrices of size (n1, n2) (coordinates of a set of points). dir a string, parameter used to specify the conversion type (See "Description" for details). x1, y1 two matrices of size (n1, n2) (coordinates of the set of points). rect a vector of size 4. After having used a graphics function, xchange computes pixel coordinates from real coordinates and conversely, according to the value of the parameter dir: "f2i" (float to int) means real to pixel and "i2f" (int to float) means pixel to real. x1 and y1 are the new coordinates of the set of points defined by the old coordinates x and y. rect is the coordinates in pixel of the rectangle in which the plot was done: [upper-left point, width, height].