Match zdata cursor display scalling with colorbar ?

Hello,

With Matplotlib 1.5.0, zdata to the cursor is displayed in the status bar. It is a very good new feature.
But, this zdata is the base data value, and this don't match if a scalling is used with the colorbar.

Is it possible to scale this displayed zdata like the colorbar ? I din't found an existing function for rescale this zdata.

I think the better solution should be to default use the scaling used on the colorbar.

Thanks.

I don't quite understand what you mean. Can you provide a snippet of code which demonstrates the problem?

Sorry if I am unclear.

Here is a snippet :

import matplotlib.pyplot as plt
from mpl_toolkits.axes_grid1 import make_axes_locatable
from matplotlib.ticker import FuncFormatter
import numpy as np

# Source data
Data = np.array(((1.0, 2.0), (3.0, 4.0)))  # Data in µm
DisplayUnitFactor = 1000  # Display unit is nm

# A plot with Data (µm)
plot = plt.matshow(Data)

# Colorbar with Z scalled to unit (nm)
cbcax = make_axes_locatable(plt.gca()).append_axes("right", "10%", pad="1%")
cbformat = FuncFormatter(lambda z, pos: '{0:g}'.format(z * DisplayUnitFactor))
cbar = plt.colorbar(plot, cax=cbcax, format=cbformat)

plt.show()

In Statusbar, Z is still in µm even if my colorbar is in nm.

Ideally, FuncFormatter from the colorbar may be applied on the statusbar Z display also.

Why not just scale your data in matshow instead of doing it in the colorbar tick formatter?

Isn't that besides the point? Don't we already obtain the axis formatters
for the x and y coordinates? I think it would make sense to use the
colorbar's formatter if it is available.

On Fri, Nov 6, 2015 at 1:14 PM, Eric Firing notifications@github.com
wrote:

Why not just scale your data in matshow instead of doing it in the
colorbar tick formatter?

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Reply to this email directly or view it on GitHub
#5409 (comment)
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@JGoutin

You are right, this is a reasonable idea, and it looks easy enough for the use case here.
In backend_bases:

   2839                     a = max(enumerate(artists), key=lambda x: x[1].zorder)[1]
   2840                     if a is not event.inaxes.patch:
   2841                         data = a.get_cursor_data(event)
   2842                         if data is not None:
   2843                             s += ' [%s]' % a.format_cursor_data(data)
   2844

One can try to find a a.colorbar; if it exists and is callable, then use it in place of a.format_cursor_data.
It might also be good to allow an axes to have an fmt_zdata attribute, like fmt_xdata and fmt_ydata for setting an alternative formatter. One might not always want the formatting for the cursor display be the same as for the colorbar ticks.
@JGoutin would you like to generate a pull request along these lines? Or at least for the first part?

Side comment: it would be nice not to have so much logic executed inside mouse_move; maybe some of it can be factored out. format_cursor_data() is a generic Artist method. It could be overridden in a color-mapped artist when a colorbar is assigned to it.

Do the color mappables know what color bar they are associated with?

This seems like a very deep coupling that I am not sure we want.

In any case, the logic for this mapping should live in the artists, not the
axes.

On Fri, Nov 6, 2015, 13:32 Benjamin Root notifications@github.com wrote:

Isn't that besides the point? Don't we already obtain the axis formatters
for the x and y coordinates? I think it would make sense to use the
colorbar's formatter if it is available.

On Fri, Nov 6, 2015 at 1:14 PM, Eric Firing notifications@github.com
wrote:

Why not just scale your data in matshow instead of doing it in the
colorbar tick formatter?

—
Reply to this email directly or view it on GitHub
<
#5409 (comment)

.

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#5409 (comment)
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On 2015/11/06 9:40 AM, Thomas A Caswell wrote:

Do the color mappables know what color bar they are associated with?

Yes. Colorbar.colorbar_factory attaches the colorbar attribute to the
mappable.

would you like to generate a pull request along these lines? Or at least for the first part?

Why not. But my knowledge on mpl low level working is very poor.

One can try to find a a.colorbar; if it exists and is callable, then use it in place of a.format_cursor_data.

I tried to do this, but a.colorbar is not callable (With my snippet, in any case).

Oops! I meant to say that one looks for a callable a.colorbar.formatter.

Work good with this. I created a pull request : #5425.

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Match zdata cursor display scalling with colorbar ? #5409

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Match zdata cursor display scalling with colorbar ? #5409

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tacaswell commented on Nov 5, 2015

JGoutin commented on Nov 6, 2015

efiring commented on Nov 6, 2015

WeatherGod commented on Nov 6, 2015

efiring commented on Nov 6, 2015

efiring commented on Nov 6, 2015

tacaswell commented on Nov 6, 2015

efiring commented on Nov 6, 2015

JGoutin commented on Nov 6, 2015

efiring commented on Nov 6, 2015

JGoutin commented on Nov 6, 2015

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