Hi Brad,
I didn't quite follow what it was that you were trying to achieve, but the
following example may be of interest to you:
import matplotlib.pyplot as plt
from matplotlib.patches import Ellipse, Circle
import matplotlib.transforms as mtrans
fig = plt.figure()
ax1 = fig.add_subplot(111)
x_in_axes_coords, y_in_axes_coords = 0.5, 0.5
radius_in_axes = 0.3
coords = [[x_in_axes_coords, y_in_axes_coords],
[x_in_axes_coords + radius_in_axes, y_in_axes_coords]]
coords = ax1.transAxes.transform(coords)
x_device, y_device = coords[0, :]
radius = coords[1, 0] - x_device
circle = Circle((x_device, y_device), radius,
transform=mtrans.IdentityTransform())
fig.artists.append(circle)
plt.show()
Clearly, you will always have circles with this approach (the circle is
defined in device coordinates, i.e. pixels),
but with the way this is implemented, it does not behave in the same way as
axes coordinates do when you resize your window.
> I am trying to plot some small circles in my plotting window, in addition
to the curves I'm already plotting.
I wonder if you would mind expanding on that sentence? Does the example I
provide do what you want?
Thanks,
Phil
On 5 November 2012 20:51, Brad Malone <brad.mal...@gmail.com> wrote:
> Hello,
>
> I am trying to plot some small circles in my plotting window, in addition
> to the curves I'm already plotting. If I don't want to set my x- and y-
> axis scales equal to each other, a naive drawing of a circle results in an
> ellipse. To fix this problem I found some nice example code online here :
> http://stackoverflow.com/questions/9230389/why-is-matplotlib-plotting-my-circles-as-ovals,
> which solves the problem by basically plotting an ellipse, but an ellipse
> which will look like a circle in the display window.
>
> That works all fine for me, but then, if I change my xlim or ylim using
> ax1.set_xlim((something1,something2)) then the solution no longer works,
> and I get an ellipse.
>
> A minimal example showing the breaking behavior can be seen below.
>
>
>
> import matplotlib.pyplot as plt
>> from matplotlib.patches import Ellipse, Circle
>>
>> fig = plt.figure()
>> ax1 = fig.add_subplot(111)
>> # uncomment the following line to see it break
>> #ax1.set_xlim((0.2,1))
>>
>> # calculate asymmetry of x and y axes:
>> x0, y0 = ax1.transAxes.transform((0, 0)) # lower left in pixels
>> x1, y1 = ax1.transAxes.transform((1, 1)) # upper right in pixes
>> dx = x1 - x0
>> dy = y1 - y0
>> maxd = max(dx, dy)
>> width = .15 * maxd / dx
>> height = .15 * maxd / dy
>> # a circle you expect to be a circle, but it is not
>> ax1.add_artist(Circle((.5, .5), .15))
>> # an ellipse you expect to be an ellipse, but it's a circle
>> ax1.add_artist(Ellipse((.75, .75), width, height))
>>
>> plt.show()
>
>
> I suppose the problem is that ax1.transAxes.transform commands return the
> same numbers, regardless of whether I've changed the limits or not. Is
> there an easy and clean way to fix this (perhaps a different command for
> getting x0,y0,x1, and y1)?
>
> Thanks for the help!
>
> Best,
> Brad
>
>
>
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