Re: [Matplotlib-users] Re: text on top just below xticks

[Charles R. T. <ct...@gm...>]

John,

Thanks, that did it.  I don't really need to blend though.  What I
need it taken care of by:

#trans =3D blend_xy_sep_transform(ax.transData, ax.transAxes)
trans =3D blend_xy_sep_transform(ax.transAxes, ax.transAxes)
scale =3D fig.dpi/Value(72.) # points -> pixels
point_trans =3D scale_transform(scale, scale)
trans.set_offset((0,-ticksize-2),point_trans)
ax.text(0.5, 1, "My Title", ha=3D'center', va=3D'top', transform=3Dtrans)

It seems a bit silly to call the blend_xy transform for that (since
I'm using transAxes for both x and y), but copy.copy doesn't work, so
there we are.

Thanks again.
-C


On 1/11/06, John Hunter <jdh...@ni...> wrote:
> >>>>> "Charles" =3D=3D Charles R Twardy <ct...@gm...> writes:
>
>     Charles> I don't think so.  I looked at that.  Maybe I'm mistaken,
>     Charles> but seems that in the end, it just places the text at y
>     Charles> position 0.9 in Axes coordinates.  That's just below the
>     Charles> markers for small subplots, but WAY below the markers for
>     Charles> tall skinny ones.  I want it to place the text at a fixed
>     Charles> absolute y position of just below the markers. As the
>     Charles> graph gets taller, that will go from .9 to .95 to .99,
>     Charles> etc. in Axes coordinates.
>
>     Charles> So one approach would be to find the Axes coordinates for
>     Charles> the lower limit of the tick markers.  Any ideas?
>
> This is a bit tricky but doable.  The transformation that places the
> xticks is a "blend" of the data transform and the axes transform, in
> that the x value of the x ticks is a data coord, and the y value is an
> axes coord(0 is bottom, 1 is top).  The transform module provides a
> helper function to build such a beast
>
>   from matplotlib.transforms import blend_xy_sep_transform
>   trans =3D blend_xy_sep_transform(ax.transData, ax.transAxes)
>
>
> If you then make a call to text
>
>   ax.text(.2,1,'hi mom', transform=3Dtrans)
>
> it will be placed at the top of the yaxis at 0.2 on the xaxis.
>
>
> What you want to do is offset this by a couple of points below the
> tick like.  To do this, you need to set an offset on the transform,
> where the coordinates of the offset are in points.  The offset is
> always an xy tuple with a transform to transform that tuple into
> figure coords.  In the case of points, you want to do
>
>
>   scale =3D fig.dpi/Value(72.) # points -> pixels
>   point_trans =3D scale_transform(scale, scale)
>   trans.set_offset((0,-ticksize-2),point_trans)
>
>
>
> Here is a complete example: now when you resize the figure window or
> pan/zoom your text will remain 2 points below the ticks...
>
> from matplotlib import rcParams
> import matplotlib.numerix as nx
> from pylab import figure, show
> from matplotlib.transforms import blend_xy_sep_transform, Value, scale_tr=
ansform
>
> ticksize =3D rcParams['xtick.major.size']
>
> fig =3D figure()
> ax =3D fig.add_subplot(111)
> x,y =3D nx.mlab.rand(2,100)
> ax.plot(x,y)
> locs =3D nx.arange(0,1.0,0.2)
> ax.set_xticks(locs)
>
>
> trans =3D blend_xy_sep_transform(ax.transData, ax.transAxes)
> scale =3D fig.dpi/Value(72.) # points -> pixels
> point_trans =3D scale_transform(scale, scale)
>
> # the offset is an xy tup and a transformation instance for that tuple
> trans.set_offset((0,-ticksize-2),point_trans)
>
> for loc in locs:
>     ax.text(loc,1,'%1.1f'%loc, transform=3Dtrans, va=3D'top', ha=3D'cente=
r')
> show()
>
>


--
Charles R. Twardy