Re: [Matplotlib-users] compresson ratio

[John H. <jdh...@ac...>]

>>>>> "Alan" == Alan G Isaac <ai...@am...> writes:


    Alan> OK, this does not work for me.  Test case:
    Alan> d=arange(201)*pi/100 plot(cos(d),sin(d)) square() show()
    Alan> This should look like a circle.  It looks like an oval.

    Alan> Problems: 1. fig.set_figsize_inches is ignored.  It has no

Right, I noted this in my original post - if you continue that
post where I posted this code:

    It's the right idea, but it doesn't work currently if you are
    using a GUI backend.  The reason it fails is has to do with the
    pipeline order in which figure managers, figures etc are created
    by default, and the fact that configure events and resize events
    change the figure width and height (so you can for example, resize
    your figure window).  It *does* work if you specify the figure
    size

    figure(figsize=(8,8))

This is a bug, as I mentioned before, but will require some thought
about how to get this right across backends.

    Alan> 2. axis('equal') should not be desirable, if it is matlab
    Alan> compatible
    Alan> http://www.mathworks.com/access/helpdesk/help/techdoc/ref/axis.html
    Alan> That is, square() should set an axis aspect ratio of unity,
    Alan> but axis('equal') should equate the *unit length* along each
    Alan> axis.  (For my example circle this is not a problem, but in
    Alan> generaly this is completely wrong.)

With the amended axes code I'm attaching below, does this example work
as you hope

    from matplotlib.matlab import *
    figure(figsize=(8,8))
    ax = axes([0.1, 0.1, 0.8, 0.8])
    d=arange(201)*pi/100
    plot(10+cos(d),sin(d))
    axis('equal')
    show()

Perhaps more typing than you want for an interactive demo, but does
make everything clear and should work, at least up to the dpix/dpiy
error we discussed earlier.

If it works fine, I'll make it a FAQ.  I still have to handle the case
where the axis lim are decreasing...

JDH

def axis(*v):
    """
    axis() returns the current axis as a length a length 4 vector

    axis(v) where v= [xmin xmax ymin ymax] sets the min and max of the
    x and y axis limits

    axis('off') turns off the axis lines and labels

    axis('equal') sets the xlim width and ylim height to be to be
    identical.  The longer of the two intervals is chosen
    """
    
    if len(v)==1 and is_string_like(v[0]):
        s = v[0]
        if s.lower()=='on': gca().set_axis_on()
        elif s.lower()=='off': gca().set_axis_off()
        elif s.lower()=='equal':
            ax = gca()
            xmin, xmax = ax.get_xlim()
            ymin, ymax = ax.get_ylim()            
            width = xmax-xmin
            height = ymax-ymin
            # TODO: handle decreasing lim
            
            interval = max([width, height])
            ax.set_xlim((xmin, xmin+interval))
            ax.set_ylim((ymin, ymin+interval))            
            draw_if_interactive()
            
        else:
            error_msg('Unrecognized string %s to axis; try on or off' % s)
        return
    
    try: v[0]
    except IndexError:
        xlim = gca().get_xlim()
        ylim = gca().get_ylim()
        return [xlim[0], xlim[1], ylim[0], ylim[1]]
    
    v = v[0]
    if len(v) != 4:
        error_msg('v must contain [xmin xmax ymin ymax]')
        return 
    gca().set_xlim([v[0], v[1]])
    gca().set_ylim([v[2], v[3]])
    draw_if_interactive()