From: John Hunter <jdhunter@ac...>  20050131 20:01:53

>>>>> "Dominique" == Dominique Orban <Dominique.Orban@...> writes: Dominique> Regarding the use of transforms in Matplotlib, what Dominique> would be the simplest way to convert a quantity Dominique> expressed in data coordinates to points and conversely? Dominique> Are the methods gca().transData.xy_tup() and Dominique> inverse_xy_tup() what I'm looking for? If so, how Dominique> should I be calling them? I think the easiest way is to transform the data to screen coordinates and then apply a scale factor to convert pixels to points. All of the transform methods xy_tup(xy)  transform the tuple (x,y) seq_x_y(x, y)  transform the python sequences x and y numerix_x_y(x, y)  x and y are numerix 1D arrays seq_xy_tups(seq)  seq is a sequence of xy tuples return screen coords. To get points from left, bottom, you would could convert to inches by dividing by dpi, and then multiply by the number of points per inch. Untested, off the cuff, but should be right: # display coords dx, dy = trans.xy_tup(x, y) # points from left of figure window px = dx/dpi*72 # points from bottom of figure window py = dy/dpi*72 with the usual caveat that screen dpi is not the same in the x and y directions so the physical units may not be exact when displayed. JDH 