Turns even the largest data into images, accurately

Datashader is a graphics pipeline system for creating meaningful representations of large datasets quickly and flexibly. Datashader breaks the creation of images into a series of explicit steps that allow computations to be done on intermediate representations. This approach allows accurate and effective visualizations to be produced automatically without trial-and-error parameter tuning, and also makes it simple for data scientists to focus on particular data and relationships of interest in a principled way.

The computation-intensive steps in this process are written in Python but transparently compiled to machine code using Numba and flexibly distributed across cores and processors using Dask, providing a highly optimized rendering pipeline that makes it practical to work with extremely large datasets even on standard hardware.

To make it concrete, here's an example of what Datashader code looks like:


import datashader as ds, pandas as pd
import datashader.transfer_functions as tf
df = pd.read_csv('user_data.csv')

cvs = ds.Canvas(plot_width=400, plot_height=400)
agg = cvs.points(df, 'x_col', 'y_col', ds.mean('z_col'))
img = tf.shade(agg, cmap=['lightblue', 'darkblue'], how='log')


This code reads a data file into a Pandas dataframe df, and then projects the fields x_col and y_col onto the x and y dimensions of 400x400 grid, aggregating it by the mean value of the z_col of each datapoint. The results are rendered into an image where the minimum count will be plotted in lightblue, the maximum in darkblue, and ranging logarithmically in between.

With code like the above, you can plot 300 million points of data (one per person in the USA) from the 2010 census without any parameter tuning:

image

image

Or you can plot attractors with 10 million points each, using random colormaps:

image

See the topics page for these and many other examples.

Installation

Please follow the instructions on Getting Started if you want to reproduce the specific examples on this website, or follow the instructions at PyViz.org if you want to try out Datashader together with related plotting tools.

Other resources

You can watch a short talk about datashader on YouTube: Datashader: Revealing the Structure of Genuinely Big Data. or listen to the Open Source Directions episode from July 2019.

Some of the original ideas for datashader were developed under the name Abstract Rendering, which is described in a 2014 SPIE VDA paper.

The source code for datashader is maintained at our Github site, and is documented using the API link on this page.

We recommend the Getting Started Guide to learn the basic concepts and start using Datashader as quickly as possible.

The User Guide covers specific topics in more detail.

The API is the definitive guide to each part of Datashader, but the same information is available more conveniently via the help() command as needed when using each component.

Please feel free to report issues or contribute code. You are also welcome to chat with the developers on gitter.