Adding a colorbar --- how?

Virgil_Stokes · June 15, 2014, 10:17pm

There are some rather nice and useful matplotlib examples for
colormaps that are shown at:

In, how can one add a colorbar?

–V

···

http://nbviewer.ipython.org/github/dpsanders/matplotlib-examples/blob/master/colorline.ipynb
** Example 1. Sine wave colored by time (uses the defaults for
colorline)**

Raymond_Smith · June 15, 2014, 10:46pm

Hi Virgil,

I did something very much like this recently by simply adding an axes to my figure and using it to show a linspace of the data range off which the line color was based. See http://matplotlib.org/examples/color/colormaps_reference.html.

Best,
Ray

···

On Sun, Jun 15, 2014 at 6:17 PM, Virgil Stokes <vs@…2650…> wrote:

There are some rather nice and useful matplotlib examples for
colormaps that are shown at:

http://nbviewer.ipython.org/github/dpsanders/matplotlib-examples/blob/master/colorline.ipynb
In **      Example 1.  Sine wave colored by time (uses the defaults for
colorline)**, how can one add a colorbar?
--V

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Eric_Firing1 · June 15, 2014, 11:12pm

There are some rather nice and useful matplotlib examples for colormaps
that are shown at:

http://nbviewer.ipython.org/github/dpsanders/matplotlib-examples/blob/master/colorline.ipynb

In*Example 1. Sine wave colored by time (uses the defaults for
colorline)*, how can one add a colorbar?

lc = colorline(x, y)
cbar = fig.colorbar(lc)

Eric

···

On 2014/06/15, 12:17 PM, Virgil Stokes wrote:

--V

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Virgil_Stokes · June 15, 2014, 11:13pm

Thanks for your response to my request, Ray. I had looked at this
approach earlier; but, what I really need is something like is
produced by the following code for the cax object:
But, for a colorline object, which was referenced in the link given
in my earlier email.
–V

···

On 16-Jun-14 00:46, Raymond Smith
wrote:

Hi Virgil,
      I did something very much like this recently by simply adding
an axes to my figure and using it to show a linspace of the
data range off which the line color was based. See http://matplotlib.org/examples/color/colormaps_reference.html.

Best,

    Ray



        On Sun, Jun 15, 2014 at 6:17 PM,

Virgil Stokes <vs@…4541…>
wrote:

            There are some

rather nice and useful matplotlib examples for colormaps
that are shown at:

            [http://nbviewer.ipython.org/github/dpsanders/matplotlib-examples/blob/master/colorline.ipynb](http://nbviewer.ipython.org/github/dpsanders/matplotlib-examples/blob/master/colorline.ipynb)

            In **                  Example 1.  Sine wave colored by time (uses the

defaults for colorline)** , how can one add a
colorbar?

--V

          HPCC Systems Open Source Big Data Platform from LexisNexis

Risk Solutions

          Find What Matters Most in Your Big Data with HPCC Systems

          Open Source. Fast. Scalable. Simple. Ideal for Dirty Data.

          Leverages Graph Analysis for Fast Processing & Easy

Data Exploration

          [http://p.sf.net/sfu/hpccsystems](http://p.sf.net/sfu/hpccsystems)

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          Matplotlib-users@lists.sourceforge.net

          [https://lists.sourceforge.net/lists/listinfo/matplotlib-users](https://lists.sourceforge.net/lists/listinfo/matplotlib-users)

`“”"Produce custom labelling for a colorbar.``

``

`` Original Script:  Scott Sinclair``

``    Modification:  V. Stokes``

``"""``

``

``import matplotlib.pyplot as plt``

``import numpy             as np``

``import matplotlib.colors as col``

``from matplotlib   import cm``

``from numpy.random import randn``

``

``def register_cmap():``

``    """``

``           Purpose: define colormap using the from_List() method

as a ``

``              segmented list and register it.``

``    """``

``    cmap_Name  = 'reyegr'    # my colormap name``

``    startcolor = '#00AF33'   # truegreen    ``

``          midcolor   = '#FFE600'   # yolk (a medium dark

yellow) ``

``    endcolor   = '#FF0033'   # bright red``

``          cmap2 =

col.LinearSegmentedColormap.from_list(cmap_Name,``

``

[startcolor,midcolor,endcolor])``

``    cm.register_cmap(cmap=cmap2)``

``          return cm.get_cmap(cmap_Name)  # my new cmap for

‘reylgr’``

``

``#-----------------------------------------------------------------------------``

``my_cmap = register_cmap()``

``

``## Vertical colorbar-1``

``fig, ax = plt.subplots()``

``

``data = np.clip(randn(250, 250), -1, 1)``

``

``      cax = ax.imshow(data, interpolation='nearest',

cmap=my_cmap)``

``ax.set_title('Gaussian noise with vertical colorbar')``

``      # Add colorbar, make sure to specify tick locations to

match desired ticklabels``

``cbar = fig.colorbar(cax, ticks=[-1, 0, 1])``

``      cbar.ax.set_yticklabels(['<-1', '0', '> 1'])#

vertically oriented colorbar``

``

``## Vertical colorbar-2``

``fig, ax = plt.subplots()``

``

``data = np.clip(randn(50, 50), -1, 1)``

``

``      #cax = ax.imshow(data, interpolation='nearest',

cmap=cm.coolwarm)``

``      cax = ax.imshow(data, interpolation='nearest',

cmap=my_cmap)``

``ax.set_title('Gaussian noise with vertical colorbar')``

``

``      # Add colorbar, make sure to specify tick locations to

match desired ticklabels``

``cbar = fig.colorbar(cax, ticks=[-1, 0, 1])``

``# Vertically oriented (by default) colorbar``

``cbar.ax.set_yticklabels(['Low', 'Medium', 'High'])``

``

``## Horizontal colorbar``

``fig, ax = plt.subplots()``

``# ``

``      cax = ax.imshow(data, interpolation='nearest',

cmap=my_cmap)``

``ax.set_title('Gaussian noise with horizontal colorbar')``

``

``      cbar = fig.colorbar(cax, ticks=[-1, 0, 1],

orientation=‘horizontal’)``

``      cbar.ax.set_xticklabels(['Low', 'Medium', 'High'])#

horizontal colorbar``

``

``plt.show()`

Virgil_Stokes · June 15, 2014, 11:21pm

This works fine --- thanks very much Eric.

Have a good day

···

On 16-Jun-14 01:12, Eric Firing wrote:

On 2014/06/15, 12:17 PM, Virgil Stokes wrote:

There are some rather nice and useful matplotlib examples for colormaps
that are shown at:

http://nbviewer.ipython.org/github/dpsanders/matplotlib-examples/blob/master/colorline.ipynb

In*Example 1. Sine wave colored by time (uses the defaults for
colorline)*, how can one add a colorbar?

lc = colorline(x, y)
cbar = fig.colorbar(lc)

Eric