Building a Data Science Capability: Inspirational Keynote at Data Leaders Summit Europe

I’ve just delivered the inspirational keynote at Data Leaders Summit Europe, 2018. Lots of great engagement and feedback. In particular, it seems people liked a clear definition of what data science actually is and the practical steps (miss-steps) I took in building a capability at Sainsbury’s.

You can find all the slides here on SlideshareAs always, if you have questions or want to discuss then please get in touch!

13 Steps to Better Data Science: A Joel Test of Data Science Maturity

Data Science teams have different levels of maturity in terms of their ways of working. In the worst case, every team member works as an individual. Results are poorly explained and impossible to reproduce. In the best case, teams reach full scientific reproducibility with simple conventions and little overhead. This leads to efficiency and confidence in results and minimal friction in productionising models. It is important to be able to measure a team’s maturity so that you can improve your ways of working and so you can attract and retain great talent. This series of questions is a Joel Test of Data Science Maturity. As with Joel’s original test for software development, all questions are a simple Yes/No and a score below 10 is cause for concern. Depressingly, many teams seem to struggle around a 3.

A Joel Test of Data Science Maturity

  1. Are results reproducible?
  2. Do you use source control?
  3. Do you create a data pipeline that you can rebuild with one command?
  4. Do you manage delivery to a schedule?
  5. Do you capture your objectives (scientific hypotheses)?
  6. Do you rebuild pipelines frequently?
  7. Do you track bugs in your models and your pipeline code?
  8. Do you analyse the robustness of your models?
  9. Do you translate model performance to commercial KPIs?
  10. Do new candidates write code at interview?
  11. Do you have access to scalable compute and storage?
  12. Can Data Scientists install libraries and packages without intervention by IT?
  13. Can Data Scientists deploy their models with minimal dependencies on engineering and infrastructure?


1. Are results reproducible?

A core aspect of traditional science is that results be reproducible. This is essential when building models of the world that aim to improve our understanding of the world. It is no different for Data Science. And it turns out the reproducibility promotes efficiency. Teams no longer waste time wondering which data led to a particular result, which code led to a particular result and why results might have changed as understanding of the problem improved.

2. Do you use source control?

Building algorithms and data pipelines is complex. Source control lets you track changes to your code, roll back poor changes and try out new ideas without breaking working code.

3. Do you create a data pipeline that you can rebuild with one command?

A version controlled data pipeline allows you to centralise and consolidate your understanding of the data (business and cleaning rules) and your definition of features that feed into an algortihm. If you can rebuild this pipeline with one command then you can quickly iterate as your understanding of the problem evolves and as you inevitably discover issues with the data.

4. Do you manage delivery to a schedule?

Data science needs a schedule to keep it focused. As projects are often open ended and exploratory, you need to have clear checkpoints where you can make a call that perhaps ‘this data is not fit for purpose’ or ‘there is no value in further iterations of model refinement’. Teams that do not deliver to any schedule tend to drift into perfection being the enemy of done.

5. Do you capture your objectives?

Every data science problem is really an optimisation problem and you cannot optimse without an objective. Although it can sometimes feel painful or appear ‘picky’, it is essential that the objective of a project and a model are clearly defined. Increate profit? Increase volume? Increase both with some balance? Get clear and agree with your customer.

6. Do you rebuild pipelines often?

Like traditional software, rebuilding often can highlight integration bugs. In the context of data science integration bugs are effectively data flows through a pipeline. If you do not rebuild often it is possible to introduce cyclic references into your data preparation, lose the logic for creation of a feature and other nasty bugs that cause you to lose that essential reproducibility.

7. Do you track bugs in your model and in your pipeline code?

Data science model development is complex. It has many dependencies. Customer feedback and domain knowledge are incredibly valuable. Make sure you are tracking feedback so mistakes are not repeated and so your models are always improving.

8. Do you analyse the robustness of your models?

No model will work in all scenarios and poor performing models are dangerous. It is important to analyse and understand the conditions under which your model will work and under which it will degrade. This is robustness analysis. Are model outputs biased? Does a model require 6months of training data or 2 weeks? Does a model only perform once it has seen 5 customer journeys? A mature data science team has confidence pushing its models into production because this type of testing has been done in advance.

9. Do you translate model performance to commercial KPIs?

Technical performance metrics are important for you as a technical data scientist. However, to get business buy-in and adoption of your models you need to be able to make your models commercially relevant. That means turning predictions into revenue or cost savings or time savings or whatever the business cares about and whatever will justify further funding of your work.

10. Do new candidates write code at interview?

Data science is full of hype, bluffers and analytics rebranding itself. You want to filter down to the great candidates who understand the scientific method and can apply it to select and tune models. A technical test that involves using data and writing code is the most effective way to do this.

11. Do you have access to scalable compute and storage?

The complex combination of technologies needed for Data SCience often means that organisations struggle to enable their teams with the best technology to do their jobs. If your team does not have access to scalable compute and storage then their success will always be limited. Lack of a central place to store data and workings is a warning sign that Data Science is not taken seriously in an organisation.

12. Can data scientists install libraries and packages without intervention by IT?

If there is one word that summarises the requirements of Data Science it is ‘flexibility’. The nature of the work involves selecting models and tuning them against data. This means being able to quickly install and evaluate lots of model libraries. If a Data Science team needs approval for every library installation and upgrade then its speed of turnaround is going to slow from days to weeks and months.

13. Can Data Scientists deploy their models with minimal dependencies on engineering and infrastructure?

If models cannot be put into use they are of little value beyond curiousities. But deploying a model involves training on reproducible data, monitoring of decisions and performance and A/B testing of new releases. Delays in deployment mean models go out of date or competitive advantage is lost. The best organisations have platforms that allow model deployment to happen quickly, driven by Data Scientists.

So how do you score a 13/13?

How would your team score on a Joel Test of Data Science Maturity? This is where Guerrilla Analytics can help. Guerrilla Analytics provides guiding principles and conventions for promoting data provenance and reproducibiltiy in Data Science and Analytics work. There are guidelines on how to structure projects at every stage of the life cycle and how to consolidate knowledge in flexible data pipelines. You will also learn how to leverage techniques and tools from software engineering such as testing and source control.

10 Data Science Capabilities (and supporting tools)

People want some guidance in what can be a very overwhelming and fast moving field. Managers want to know what to buy and where to invest training. Junior data scientists, students, dev ops engineers and system administrators want to know what to learn. I will focus on the important capabilities for a Data Science team and the tools I have found useful for enabling those capabilities.

I’ve recently had several people ask me about Data Science capabilities both online and at conference talks. This post lists some of the tools I use and the capabilities they provide.

When writing Guerrilla Analytics: A Practical Approach to Working with Data I deliberately avoided mention of tools. People can be dogmatic about tools and I thought this would be a distraction from the book’s core message around principles for doing effective Data Science in dynamic real-world projects.

That said, people do want some guidance in what can be a very overwhelming and fast moving field. Managers want to know what to buy and where to invest training. Junior data scientists, students, dev ops engineers and system administrators want to know what to learn. I will focus on the important capabilities for a Data Science team and the tools I have found useful for enabling those capabilities.

1. Version control with Git and git-flow

Capability: Typically you will go through many iterations of your code and the work products your code produces. It quickly becomes impossible to track changes and reproduce earlier work without some code version control tool. This is only exacerbated when your team size is >1.

Tool: Git is a great version control system and the effort to learn its command line interface is a very worthwhile investment.

Git is incredibly flexible. However this can lead to confusion and inconsistency in how it is applied. Git-flow is a set of scripts that automate much of what you will need to do in Git subject to a particular convention that happens to be very helpful for Data Science.

2. Wrangling and persisting data with PostgreSQL

Capability:  Even if your data is small enough to fit in memory, reproducing work will involve running all those scripts into memory before you can pick up where you left off. Other team members have to do the same. This is painful and inefficient. You therefore need to persist your work (raw data, intermediate datasets and work products).

Tool: A database gives you a way to persist your workings and intermediate datasets as well as share with team members. Pick a database the is performant and flexible. I use PostgreSQL. It has an amazing set of features and this flexibility is what you want when doing Data Science.

3. Wrangling and visualizing data with PandasMatplotlib and Seaborn

Capability: Getting your head around your data and preparing it for a variety of algorithms is probably the most time-consuming and important part of the Data Science life cycle. Some preparations are easier done outside of many databases e.g. some natural language processing. Visualizing the data is really important here too.

Tool: Pick a programming language that has great data reshaping and visualization capabilities. If you work in Python, Pandas is a powerful set of data structures and algorithms for wrangling. Seaborn and Matplotlib are good places to start for visualization. And don’t waste time trying to get all these things to work together. Just use Continuum’s excellent distribution Anaconda.

Read: Python for Data Analysis: Data Wrangling with Pandas, NumPy, and IPython

4. Documentation with Markdown

Capability: Data Science is useless without communication (to your customer and within your team). You could just write a report as a Word document. There’s nothing wrong with that and it’s a format your business customers will expect. However, it would be great to have a documentation that is easy to version control and can be kept close to your project code.

Tool: Markdown is a nice platform-neutral way to document your project. Because it’s plain text it’s easy to version control (see above). And if your report isn’t too complicated you can convert it to Word from Markdown. Win.

5. Fast file manipulation, cleaning, and summarising at the command line

Capability: You get hundreds of data files. You get huge files in strange formats with broken delimiters. You want to chop these up, patch them together, change their encodings, unravel XML etc etc. No, trying to open the file in a text editor or spreadsheet is not the answer.

Tool: This is best done at a powerful command line. Linux is worth learning.

Read: Data Science at the Command Line: Facing the Future with Time-Tested Tools

6. Story telling with Jupyter Notebooks

Capability: Data Science is difficult to communicate. It’s often a slightly meandering journey with dead ends, back-tracking, unexpected insights leading to new research avenues etc. When updating your customer, you need to walk them through some of this journey using narratives interleaved with graphics and tabular data. Code files won’t do. Duplicating into Powerpoint is a lot of extra work for a quick interim update.

Tool: Jupyter allows all of the above in presentation quality. The close interleaving of analysis and documentation helps other team members join a project. And it reduces duplication when you decide it’s time to stop coding and start updating your customer.

7. Build automation with Luigi

Capability: eventually, your understanding and your code start to consolidate. There are some core datasets. They go through some agreed preparatory steps. There are some reports and algorithm datasets that you want to lock down and reproduce several times during the project. Manually running all those code files is a pain.

Tool: build automation tools allow you to automate tasks such as executing code files, creating documentation, importing and exporting data etc etc. I’ve used command line scripts (see above) and software build tools like Ant for this automation. More sophisticated tools like Luigi are now reaching a level of maturity where you could consider them for your team too.

8. Workflow tracking with JIRA

Capability: what the hell is everybody doing? Where did that data come from? Where is the conversation with the system SME that led to that business rule? Where is the deliverable from 2 weeks ago and who sent it to which customer?

Tool: workflow tracking tools like JIRA help answer all the above questions. Look for a tool that is customizable as Data Science doesn’t need all the detail of a large scale software development project. Do make sure you track where your data is coming from and what deliverables are going out the door (see Guerrilla Analytics).

9. Packaging it all up with Vagrant

Capability: the diverse nature of Data Science activities leads to a correspondingly diverse set of tools as you’ve seen above. When you get things working, you would rather not break them and you would rather not force every team member to go through the same painful installations and configurations and risk inconsistency.

Tool: Vagrant and other ‘dev ops’ tools allow you to define your tech setups and their configuration in program code. What does that mean? It means that you can build your entire technology stack and configure it by running some code. It also means that the installation of all your tools and their configuration can be version controlled. As your technology stack evolves, update your code and issue a new release to your team. If you trash your technology or need to move to other servers, everything you need to reproduce your environment has been captured and you should be back up and running in minutes.

Read: Vagrant: Up and Running

10. Putting your Data Science capabilities together – Operations with Guerrilla Analytics

I’ve covered a lot here. How do you put this all together without choking a team in conventions, rules, tools etc? How do you reduce Data Science chaos and continue to deliver iteratively and at pace? That’s where Guerrilla Analytics can help.

Have a read around this blog, check out the book and start building your Data Science Capabilities!