Interactive Plotting in IPython Notebook (Part 2/2): Plotly

Summary

In this previous post I talked about interactive plotting packages that support the IPython Notebook and focused on Bokeh. Today I’ll be talking about Plotly, a much richer package that allows for a lot more functionality. I will also provide some very rudimentary examples that should allow you to get started straight away.

Plotly

Plotly is in a lot of ways similar to Bokeh of which I’ve spoken in the previous post . However, I personally find it to be prettier, sexier, more convenient, offering much more functionality, and altogether a more well-rounded solution to your interactive plotting needs.

Not only does it offer a lot of ‘basic’ 2D plot types, while I know for a fact that the devs have been working on 3D plots as well, but it allows for real-time streaming data plots, online editing of your plots and data, a slew of APIs for different languages, and a whole wealth of features which you just can’t find elsewhere.

On the other hand, Plotly isn’t entirely free. Sure the basic free plan allows you to create as many plots as you want but they’re all public and can be viewed by anyone. Should you want privacy, however, you gotta pony up the dough, and at 12$/month one might find it kinda steep. In addition, unlike Bokeh , which serves the plots locally, Plotly does so through their own servers (unless you go for an enterprise-behind-my-own-firewall-solution) and needs to upload your data to do so. Thus, get ready for some notable lag.

Nonetheless, Plotly is a gorgeous lil’ tool and IMHO in a league of its own among other tools, both in terms of features and ease of use.

Installation

At the time of writing, Plotly isn’t hosted on the conda repos so one has to install it through the pip package manager simply with:

pip install plotly

Upon successful installation, the package should now be available for import for IPython console and IPython Notebook sessions.

The aforementioned conda repos can be found here for different platforms but one can easily use the conda search command and see whether a particular package, and which versions of said package, exists within the repos.

Setup

Before you start toying with Plotly, you need to create a new account, which is free, and sign in.

Upon doing so, click on the upper-right corner at your username and go to ‘Settings’. In the window that pops up, under the ‘Profile’ tab you will see two entries which you should take note of. The username and API Key are necessary to log onto Plotly from Python as we’ll see in the Usage section below.

Usage

As an example I chose to simply redo the simple sine wave plot I showed on the previous post about Bokeh. After all, this post merely aims to showcase Plotly and as you’ll see in the next section, the good Plotly folk have create a gorgeous and extensive doc-base.

Similarly to the previous post I once more assume that you’re working directly in an IPython Notebook. This is actually important y’all as we have to use a different ‘plotting function’ as I’ll explain below.

We simply begin by importing plotly and numpy to calculate and plot a sine wave as such:

import numpy
import plotly

Next, we need to sign in to Plotly using the username and API Key which you should have retrieved during the steps described in the Setup section. Now in order to sign in you merely need a command such as the below:

plotly.plotly.sign_in("<enter your username here>", "<enter your API key here>")

At the time of writing the above function won’t return an error upon failure to log in. However, when you try to plot something you will most likely get an HTTPError: 500 Server Error: INTERNAL SERVER ERROR error, so make sure your credentials are correct.

As in the previous post, we use NumPy to calculate the ‘coordinates’ of a sine wave as such:

x = numpy.arange(0.0, 100.0, 0.1)
y = numpy.sin(x)

Now we just need to create a ‘trace’ as its called in the Plotly lingo using the Scatter function of the graph_objs module, passing the calculated coordinates:

trace0 = plotly.graph_objs.Scatter(x=x,y=y, name="Sin")

The graph_objs module contains a tremendous variety of plot types. Visit the Plotly Python API documentation for a slew of examples.

Lastly, we pass a list of such traces to a one of the different ‘plot functions’ which reside under the plotly.plotly module. The one we need to use for an IPython Notebook is the iplot function which will return an IPython.core.display.HTML object and force the resulting plot to appear as the output of the current cell. For this case the call is the following:

plotly.plotly.iplot([trace0])

This last command will, after a few seconds, return an output that should look like the figure below. I’d like you to note the tools on the upper-right corner of the plot which allow for panning, zooming, and controlling the hover-tooltip behavior. In addition, by clicking on the plotly - data and graph >> link in the lower-right corner, you’ll be taken to the Plotly website where you can edit/format the plot, view/edit the data that generated, as well as share it with others.

Note that by using the plotly.plotly.plot function instead of plotly.plotly.iplot you will be taken directly to the Plotly website as if you clicked on the plotly - data and graph >> link.

You can find an IPython Notebook with the code used to create the above plot here. Note that even though I’ve removed my credentials from the plotly.plotly.sign_in call, the plot should still show as its linking directly to that figure on the Plotly website.

Resources

The Plotly people have created a beautiful learn page which has a ton of info including tutorials and guides.

Since here we’re entirely focusing on Python, take a look at the corresponding Getting Started page and the Plotly for Python User Guide. In addition, the nbviewer contains a section dedicated to Plotly which is pretty much a notebook’ed version of the aforementioned User Guide.

Lastly, the Plotly Python API documentation has a slew of examples with the accompanying stand-alone source code which is generated explicitly for your username and contains the necessary key you need to log in.