There is now a section of the documentation describing [how color mapping and normalization works][1] 

The way that `matplotlib` does color mapping is in two steps, first a `Normalize` function (wrapped up by the sub-classes of `matplotlib.colors.Normalize`) which maps the data you hand in to `[0, 1]`.  The second step maps values in `[0,1]` -&gt; RGBA space.  

You just need to use the `LogNorm` normalization class, passed in with the `norm` kwarg.

    plt.scatter(x,y,edgecolors=&#39;none&#39;,s=marker_size,c=void_fraction,
                    norm=matplotlib.colors.LogNorm())

When you want to scale/tweak data for plotting, it is better to let `matplotlib` do the transformations than to do it your self.


 - `Normalize` [doc][2]
 - `LogNorm` [doc][3]
 - `matplotlib.color` [doc][4] 


  [1]: https://matplotlib.org/stable/tutorials/colors/colormapnorms.html
  [2]: http://matplotlib.org/api/colors_api.html#matplotlib.colors.Normalize
  [3]: http://matplotlib.org/api/colors_api.html#matplotlib.colors.LogNorm
  [4]: http://matplotlib.org/api/colors_api.html#module-matplotlib.colors

I&#39;m trying to apply a background image to a div by using the angular `ng-style` ( I tried a custom directive before with the same behaviour ), but it doesn&#39;t seem to be working.

    &lt;nav
		class=&quot;navigation-grid-container&quot;
		data-ng-class=&quot;{ bigger: isNavActive == true }&quot;
		data-ng-controller=&quot;NavigationCtrl&quot;
		data-ng-mouseenter=&quot;isNavActive = true; $parent.isNavActive = true&quot;
		data-ng-mouseleave=&quot;isNavActive = false; $parent.isNavActive = false&quot;
		data-ng-show=&quot;$parent.navInvisible == false&quot;
		data-ng-animate=&quot;&#39;fade&#39;&quot;
		ng-cloak&gt;
		
		&lt;ul class=&quot;navigation-container unstyled clearfix&quot;&gt;
			&lt;li
				class=&quot;navigation-item-container&quot;
				data-ng-repeat=&quot;(key, item) in navigation&quot;
				data-ng-class=&quot;{ small: $parent.isNavActive, big: isActive == true }&quot;
				data-ng-mouseenter=&quot;isActive = true; isInactive= false&quot;
				data-ng-mouseleave=&quot;isActive = false; isInactive= true&quot;&gt;
				
				&lt;div data-ng-switch on=&quot;item.id&quot;&gt;

					&lt;div class=&quot;navigation-item-default&quot; data-ng-switch-when=&quot;scandinavia&quot;&gt;
						&lt;a class=&quot;navigation-item-overlay&quot; data-ng-href=&quot;{{item.id}}&quot;&gt;
							&lt;div class=&quot;navigation-item-teaser&quot;&gt;
								&lt;span class=&quot;navigation-item-teaser-text&quot; data-ng-class=&quot;{ small: isScandinavia }&quot;&gt;{{item.teaser}}&lt;/span&gt;
							&lt;/div&gt;
						&lt;/a&gt;
						&lt;span class=&quot;navigation-item-background&quot; data-ng-style=&quot;{ &#39;background-image&#39;: &#39;public/img/products/{{item.id}}/detail/wide/{{item.images.detail.wide[0]}}&#39; }&quot;&gt;&lt;/span&gt;
					&lt;/div&gt;

					&lt;div class=&quot;navigation-item-last&quot; data-ng-switch-when=&quot;static&quot;&gt;
						&lt;div class=&quot;navigation-item-overlay&quot;&gt;
							&lt;div class=&quot;navigation-item-teaser&quot;&gt;
								&lt;span class=&quot;navigation-item-teaser-text&quot;&gt;
									&lt;img data-ng-src=&quot;{{item.teaser}}&quot;&gt;
								&lt;/span&gt;
							&lt;/div&gt;
						&lt;/div&gt;
						&lt;span class=&quot;navigation-item-background&quot;&gt;
							&lt;img class=&quot;logo&quot; data-ng-src=&quot;{{item.images.logo}}&quot;&gt;
						&lt;/span&gt;
					&lt;/div&gt;

					&lt;div class=&quot;navigation-item-default&quot; data-ng-switch-default&gt;
						&lt;a class=&quot;navigation-item-overlay&quot; data-ng-href=&quot;{{item.id}}&quot;&gt;
							&lt;div class=&quot;navigation-item-teaser&quot;&gt;
								&lt;span class=&quot;navigation-item-teaser-text&quot;&gt;{{item.teaser}}&lt;/span&gt;
							&lt;/div&gt;
						&lt;/a&gt;
						&lt;span class=&quot;navigation-item-background&quot; data-ng-style=&quot;{ &#39;background-image&#39;: &#39;public/img/products/{{item.id}}/detail/wide/{{item.images.detail.wide[0]}}&#39; }&quot;&gt;&lt;/span&gt;
					&lt;/div&gt;

				&lt;/div&gt;
			&lt;/li&gt;
		&lt;/ul&gt;
	&lt;/nav&gt;

Though, if I do try a background color, it seems to be working fine. I tried a remote source and a local source too `http://lorempixel.com/g/400/200/sports/`, neither worked.

angularjs ng-style: background-image isn&#39;t working

In CSS it is possible to style `placeholder` text within an input using a combination of vendor-specific pseudo-classes and pseudo-elements (to get the best cross-browser coverage).

These all share the same basic properties (ie: text styling and color declarations).

However whilst I inevitably want to apply the same styles irrespective of browser vendor, it doesn&#39;t appear to be possible to combine these together into a comma-separated selector (as you would with any other piece of CSS where you want two selectors to share the same styles).

As an example, I tend to target placeholder styling using the four following selectors:

 - `input:-moz-placeholder`
 - `input::-moz-placeholder`
 - `input:-ms-input-placeholder`
 - `input::-webkit-input-placeholder`

(although `:-moz-placeholder` [is being deprecated][1] in favor of `::-moz-placeholder` this only occurred with the release of FireFox 19 so at present both are needed for better browser-support). 

What&#39;s frustrating is that declaring and giving each (the same) style leads to a lot of repetition within the CSS.

So, to make sure that placeholder text is right-aligned and italic, I would end up with:

&lt;!-- language-all: lang-css --&gt;

    input:-moz-placeholder{
        font-style: italic;
        text-align: right;
    }
    input::-moz-placeholder{
        font-style: italic;
        text-align: right;
    }
    input:-ms-input-placeholder{
        font-style: italic;
        text-align: right;
    }
    input::-webkit-input-placeholder{
        font-style: italic;
        text-align: right;
    }

What I really want to do is to combine them as one single comma-seperated rule set like this:

    input:-moz-placeholder,
    input::-moz-placeholder,
    input:-ms-input-placeholder,
    input::-webkit-input-placeholder{
        font-style: italic;
        text-align: right;
    }

However, despite trying this on a fair few occasions, this never seems to work.  It makes me concerned that there&#39;s some fundamental part of CSS that I&#39;m not understanding.

Can anybody shed any light on why this happens?


  [1]: https://developer.mozilla.org/en-US/docs/Web/CSS/:-moz-placeholder

Why isn&#39;t it possible to combine vendor-specific pseudo-elements/classes into one rule set?

I would like to make the colors of the points on the scatter plot correspond to the value of the void fraction, but on a logarithmic scale to amplify differences. I did this, but now when I do plt.colorbar(), it displays the log of the void fraction, when I really want the actual void fraction. How can I make a log scale on the colorbar with the appropriate labels of the void fraction, which belongs to [0.00001,1]?

Here is an image of the plot I have now, but the void fraction colorbar is not appropriately labeled to correspond to the true void fraction, instead of the log of it.

![current plot][1]


    fig = plt.figure()
    plt.scatter(x,y,edgecolors=&#39;none&#39;,s=marker_size,c=np.log(void_fraction))
    plt.colorbar()
    plt.title(&#39;Colorbar: void fraction&#39;)

Thanks for your help.


  [1]: http://i.stack.imgur.com/k0QMe.png

A logarithmic colorbar in matplotlib scatter plot

I would like to make the colors of the points on the scatter plot correspond to the value of the void fraction, but on a logarithmic scale to amplify differences. I did this, but now when I do plt.colorbar(), it displays the log of the void fraction, when I really want the actual void fraction. How can I make a log scale on the colorbar with the appropriate labels of the void fraction, which belongs to [0.00001,1]?
Here is an image of the plot I have now, but the void fraction colorbar is not appropriately labeled to correspond to the true void fraction, instead of the log of it.
<img src="http://i.stack.imgur.com/k0QMe.png" alt="current plot">
<pre><code class="hljs language-ini">fig = plt.figure()
plt.scatter(x,y,edgecolors='none',s=marker_size,c=np.log(void_fraction))
plt.colorbar()
plt.title('Colorbar: void fraction')
</code></pre>
Thanks for your help.

I get some rather unexpected behavior on an expression that works with `==` but not with `is`:

    &gt;&gt;&gt; (True == False) is False
    True
    &gt;&gt;&gt; True == (False is False)
    True
    &gt;&gt;&gt; True == False is False
    False
    &gt;&gt;&gt; id(True)
    8978640
    &gt;&gt;&gt; id(False)
    8978192
    &gt;&gt;&gt; id(True == False)
    8978192
    &gt;&gt;&gt; id(False is False)
    8978640

Why does `True == False is False` evaluate to False?

I&#39;m still kinda new with Python, using Pandas, and I&#39;ve got some issues debugging my Python script.

I&#39;ve got the following warning message :

    [...]\pandas\core\index.py:756: UnicodeWarning: Unicode equal comparison failed to convert both arguments to Unicode - interpreting them as being unequal
    return self._engine.get_loc(key)

And can&#39;t find where it&#39;s from.

After some research, I tried to do that in the Pandas lib file (index.py):

    try:
        return self._engine.get_loc(key)
    except UnicodeWarning:
        warnings.warn(&#39;Oh Non&#39;, stacklevel=2)

But that didn&#39;t change anything about the warning message.

How to find out where a Python Warning is from

Let&#39;s say I have:

    action = &#39;{bond}, {james} {bond}&#39;.format(bond=&#39;bond&#39;, james=&#39;james&#39;)

this wil output:

    &#39;bond, james bond&#39; 


Next we have:

     action = &#39;{bond}, {james} {bond}&#39;.format(bond=&#39;bond&#39;)

this will output:

    KeyError: &#39;james&#39;


Is there some workaround to prevent this error to happen, something like:

- if keyrror: ignore, leave it alone (but do parse others)
- compare format string with available named arguments, if missing then add


Format string unused named arguments

SQLAlchemy&#39;s &lt;a href=&quot;http://docs.sqlalchemy.org/en/rel_0_8/orm/query.html#sqlalchemy.orm.query.Query.distinct&quot;&gt;Query.distinct&lt;/a&gt; method is behaving inconsistently:

    &gt;&gt;&gt; [tag.name for tag in session.query(Tag).all()]
    [u&#39;Male&#39;, u&#39;Male&#39;, u&#39;Ninja&#39;, u&#39;Pirate&#39;]
    &gt;&gt;&gt; session.query(Tag).distinct(Tag.name).count()
    4
    &gt;&gt;&gt; session.query(Tag.name).distinct().count()
    3

So the second form gives the correct result but the first form does not.  This appears to happen with SQLite but NOT with Postgres.  I have a function which is passed a query object to have a `distinct` clause applied to it, so it would be highly difficult to rewrite everything top use the second approach above.  Is there something obvious that I&#39;m missing?

Returning distinct rows in SQLAlchemy with SQLite

I use &quot;$ipython notebook --pylab inline&quot; to start the ipython notebook.  The display matplotlib figure size is too big for me, and I have to adjust it manually.  How to set the default size for the figure displayed in cell?


How to set the matplotlib figure default size in ipython notebook?

I created a 4D scatter plot graph to represent different temperatures in a specific area. When I create the legend, the legend shows the correct symbol and color but adds a line through it. The code I&#39;m using is:

    colors=[&#39;b&#39;, &#39;c&#39;, &#39;y&#39;, &#39;m&#39;, &#39;r&#39;]
    lo = plt.Line2D(range(10), range(10), marker=&#39;x&#39;, color=colors[0])
    ll = plt.Line2D(range(10), range(10), marker=&#39;o&#39;, color=colors[0])
    l = plt.Line2D(range(10), range(10), marker=&#39;o&#39;,color=colors[1])
    a = plt.Line2D(range(10), range(10), marker=&#39;o&#39;,color=colors[2])
    h = plt.Line2D(range(10), range(10), marker=&#39;o&#39;,color=colors[3])
    hh = plt.Line2D(range(10), range(10), marker=&#39;o&#39;,color=colors[4])
    ho = plt.Line2D(range(10), range(10), marker=&#39;x&#39;, color=colors[4])
    plt.legend((lo,ll,l,a, h, hh, ho),(&#39;Low Outlier&#39;, &#39;LoLo&#39;,&#39;Lo&#39;, &#39;Average&#39;, &#39;Hi&#39;, &#39;HiHi&#39;, &#39;High Outlier&#39;),numpoints=1, loc=&#39;lower left&#39;, ncol=3, fontsize=8)

I tried changing `Line2D` to `Scatter` and `scatter`. `Scatter` returned an error and `scatter` changed the graph and returned an error.

With `scatter`, I changed the `range(10)` to the lists containing the data points. Each list contains either the x, y, or z variable.

    lo = plt.scatter(xLOutlier, yLOutlier, zLOutlier, marker=&#39;x&#39;, color=colors[0])
    ll = plt.scatter(xLoLo, yLoLo, zLoLo, marker=&#39;o&#39;, color=colors[0])
    l = plt.scatter(xLo, yLo, zLo, marker=&#39;o&#39;,color=colors[1])
    a = plt.scatter(xAverage, yAverage, zAverage, marker=&#39;o&#39;,color=colors[2])
    h = plt.scatter(xHi, yHi, zHi, marker=&#39;o&#39;,color=colors[3])
    hh = plt.scatter(xHiHi, yHiHi, zHiHi, marker=&#39;o&#39;,color=colors[4])
    ho = plt.scatter(xHOutlier, yHOutlier, zHOutlier, marker=&#39;x&#39;, color=colors[4])
    plt.legend((lo,ll,l,a, h, hh, ho),(&#39;Low Outlier&#39;, &#39;LoLo&#39;,&#39;Lo&#39;, &#39;Average&#39;, &#39;Hi&#39;, &#39;HiHi&#39;,     &#39;High Outlier&#39;),scatterpoints=1, loc=&#39;lower left&#39;, ncol=3, fontsize=8)

When I run this, the legend no longer exists, it is a small white box in the corner with nothing in it. 

Any advice?

Matplotlib scatter plot legend

Does anyone know a way to bring a scatter plot to the foreground in matplotlib? I have to display the scatter plotting on top of the contour, but by default it is plotted underneath...

Thanks in advance!

Matplotlib: Scatter Plot to Foreground on top of a Contour Plot

If you want to insert a small plot inside a bigger one you can use [Axes][1], like [here][2].

The problem is that I don&#39;t know how to do the same inside a subplot.

I have several subplots and I would like to plot a small plot inside each subplot.
The example code would be something like this:


    import numpy as np
    import matplotlib.pyplot as plt

    fig = plt.figure()

    for i in range(4):
        ax = fig.add_subplot(2,2,i)
        ax.plot(np.arange(11),np.arange(11),&#39;b&#39;)

        #b = ax.axes([0.7,0.7,0.2,0.2]) 
        #it gives an error, AxesSubplot is not callable

        #b = plt.axes([0.7,0.7,0.2,0.2])
        #plt.plot(np.arange(3),np.arange(3)+11,&#39;g&#39;)
        #it plots the small plot in the selected position of the whole figure, not inside the subplot

Any ideas?

Thanks in advance!


  [1]: http://scipy-lectures.github.io/intro/matplotlib/matplotlib.html#axes
  [2]: http://matplotlib.org/examples/pylab_examples/axes_demo.html

Embedding small plots inside subplots in matplotlib

I have a range of points x and y stored in numpy arrays.
Those represent x(t) and y(t) where t=0...T-1

I am plotting a scatter plot using

    import matplotlib.pyplot as plt

    plt.scatter(x,y)
    plt.show()

I would like to have a colormap representing the time (therefore coloring the points depending on the index in the numpy arrays) 

What is the easiest way to do so?

Content Type	Original Author	Original Content on Stackoverflow
Question	Cokes	View Question on Stackoverflow
Solution 1 - Python	tacaswell	View Answer on Stackoverflow

A logarithmic colorbar in matplotlib scatter plot

Python Problem Overview

Python Solutions

Solution 1 - Python

Why isn't it possible to combine vendor-specific pseudo-elements/classes into one rule set?

angularjs ng-style: background-image isn't working

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