The real prerequisite for machine learning isn’t math, it’s data analysis

May 16, 2016
By

(This article was first published on r-bloggers – SHARP SIGHT LABS, and kindly contributed to R-bloggers)

When beginners get started with machine learning, the inevitable question is “what are the prerequisites? What do I need to know to get started?”

And once they start researching, beginners frequently find well-intentioned but disheartening advice, like the following:

You need to master math. You need all of the following:
– Calculus
– Differential equations
– Mathematical statistics
– Optimization
– Algorithm analysis
– and
– and
– and ……..

A list like this is enough to intimidate anyone but a person with an advanced math degree.

It’s unfortunate, because I think a lot of beginners lose heart and are scared away by this advice.

If you’re intimidated by the math, I have some good news for you: in order to get started building machine learning models (as opposed to doing machine learning theory), you need less math background than you think (and almost certainly less math than you’ve been told that you need). If you’re interested in being a machine learning practitioner, you don’t need a lot of advanced mathematics to get started.

But you’re not entirely off the hook.

There are still prerequisites. In fact, even if you can get by without having a masterful understanding of calculus and linear algebra, there are other prerequisites that you absolutely need to know (thankfully, the real prerequisites are much easier to master).

Math is not the primary prerequisite for machine learning

If you’re a beginner and your goal is to work in industry or business, math is not the primary prerequisite for machine learning. That probably stands in opposition to what you’ve heard in the past, so let me explain.

Most advice on machine learning is from people who learned data science in an academic environment.

Before I go on, I want to emphasize that this is not a jab. Using the term “academic” is not meant to be an insult. People who work in academia frequently build the tools that people in industry use. And through research, they also push the field forward. I admire these people.

However, there are different incentives in an academic environment. Those incentives shape the mindset and work of people in academia differently than the incentives of people who work in industry. Moreover, the incentives shape the training of people entering academia: students in an academic environment are trained to be productive largely as scholars and researchers.

In an academic environment, individuals are rewarded (largely) for producing novel research, and in the context of ML, that truly does require a deep understanding of the mathematics that underlies machine learning and statistics.

In industry though, in most cases, the primary rewards aren’t for innovation and novelty. In industry, you’re rewarded for creating business value. In most cases, particularly at entry levels, this means applying existing, “off the shelf” tools. The critical fact here, is that existing tools almost all take care of the math for you.

“Off the shelf” tools take care of the math for you

Almost all of the common machine learning libraries and tools take care of the hard math for you. This includes R’s caret package as well as Python’s scikit-learn. This means that it’s not absolutely necessary to know linear algebra and calculus to get them to work.

There’s a good quote about this by Andrew Gelman in his highly regarded book on regression:

“Most books define regression in terms of matrix operations. We avoid much of this matrix algebra for the simple reason that it is now done automatically by computers …. [the computations] are important but can be done out of sight of the user.”

Keep in mind that Gelman is a very well regarded statistician. He’s a statistics professor at Columbia University (an Ivy League university) and he’s written several best-in-class books on topics like regression and Bayesian statistics. And while this quote deals specifically with regression, the same principle applies to machine learning, broadly speaking.

This point must be emphasized: modern statistical and machine learning software takes care of much of the mathematics for you.

This means that it’s possible for you to build a good predictive model without almost any knowledge of calculus or linear algebra. If you’re still not convinced of this, then take a careful look at An Introduction to Statistical Learning or Applied Predictive Modeling. These are two excellent books on machine learning (AKA, statistical learning; AKA, model building). There’s almost no calculus or linear algebra in either of them.

This is great news for a beginning data scientist who wants to get started with machine learning. You can call an R function from caret or a function from Python’s scikit-learn and it will take care of all of the mathematics for you. Knowing how all that mathematics works “under the hood” is neither necessary nor sufficient for building predictive models as a beginner.

To be clear, I’m not suggesting that these tools do all the work for you. You still need to be well-practiced at applying them. You need to have a solid understanding of the heuristics, best practices, and rules of thumb associated with making them work well. Again though, much of the knowledge required to make these tools perform well does not require matrix algebra and calculus.

Most data scientists don’t do much math

I think many beginners have an inaccurate image in their minds of what data scientists actually do. They imagine that data scientists spend their days pensively standing at a whiteboard, scribbling math equations between sips of coffee.

2016-05-07_data-analysis-is-the-prerequisite_blackboard

That’s just not accurate.

So how much math does a data scientist actually do?

If we’re talking about entry level data scientists to intermediate level data scientists, I’d estimate that they spend less than 5% of their time actually doing mathematics. And quite frankly, 5% is probably a bit generous.

Even if we talk about machine learning only, you’ll still only spend less than 5% of your time doing math. (And quite frankly, most entry-level data scientists won’t spend much of their time on ML.) When you build a model, you will spend very, very little time doing any math.

The reality is that in industry, data scientists just don’t do much higher level math.

2016-05-07_data-analysis-is-the-prerequisite_what-a-data-scientist-is

But most data scientists do spend a huge amount of their time getting data, cleaning data, and exploring data. This applies both to data science generally, and machine learning specifically; and it particularly applies to beginners.

If you want to get started with machine learning, the real prerequisite skill that you need to learn is data analysis.

The main prerequisite for machine learning is data analysis

For beginning practitioners (i.e., hackers, coders, software engineers, and people working as data scientists in business and industry) you don’t need to know that much calculus, linear algebra, or other college-level math to get things done.

But you absolutely need to to know data analysis.

Data analysis is the first skill you need in order to get things done.

It’s the real prerequisite for getting started with machine learning as a practitioner.

(Note that as this post continues, I’m going to use the term “data analysis” as a shorthand for “getting data, cleaning data, aggregating data, exploring data, and visualizing data.”)

This is particularly true for beginners. Although at high levels there are some data scientists who need deep mathematical skill, at a beginning level – I repeat – you do not need to know calculus and linear algebra in order to build a model that makes accurate predictions.

But it will be nearly impossible to build a model if you don’t have solid skills with data analysis.

Even if you use “off the shelf” tools like R’s caret and Python’s scikit-learn – tools that do much of the hard math for you – you won’t be able to make these tools work without a solid understanding of exploratory data analysis and data visualization. In order to properly apply tools like caret and scikit-learn, you’ll need to be able to gather, prepare, and explore your data. You a need solid understanding of data analysis.

80% of your work will be data preparation, EDA, and visualization

It’s common knowledge among data scientists that “80% of your work will be data preparation.” This is true, although I want to clarify what this means. When people say that “80% of your work will be data preparation” that’s sort of a shorthand way of saying “80% of your work will be getting data (from databases, spreadsheets, flat-files), performing exploratory data analysis, reshaping data, visualizing data to find insights, and using EDA.”

While this figure is about data science in general, it also applies to machine learning specifically: when you’re building machine learning models, 80% of your time will be spent getting data, exploring it, cleaning it, and analyzing results (using data visualization).

2016-05-07_data-analysis-is-the-prerequisite_how-we-use-dataAnalysis

To be a little more blunt about it, if you don’t know calculus and linear algebra, you can still build useful models, but if you aren’t really proficient with data analysis, you’re screwed.

For beginning practitioners, data hacking beats math

This isn’t just a glib statement. Many, if not most of the best data scientists and model-builders I know at several Fortune 500 companies aren’t particularly masterful at calculus, linear algebra or advanced math. But they are exceptional at data analysis.

Here’s a personal example: one of the best predictive modelers I’ve worked with knows very little advanced math.

To be clear, she has a PhD, but her PhD is in Social Psychology. She didn’t receive training in any serious math. Based on working with her and talking with her for several years, I’m confident that her knowledge of calculus and linear algebra was very, very limited.

But, she definitely knew her way around a dataset. She knew how to explore and prepare a dataset to make machine learning algorithms work in a practical setting.

To be fair, any person with a PhD in machine learning would have smoked her when it came to explaining the underlying mathematics. She would have withered under questioning about the deep mathematical underpinnings of k-means or support vector machines. But, those things weren’t her strengths. She was a true practitioner, and she was paid quite handsomely, because she made accurate predictions. No one gave a damn about her math chops. She got results, and clients paid.

I want to emphasize that this particular friend isn’t a unicorn. I know dozens of people like this (she’s just a good example). Moreover, these practitioners aren’t employed at a “low end” companies. They all work at places like Apple and other top-tier Fortune 500 companies; companies that are crushing their goals and generating huge profits. These people are solid employees at excellent companies.

Math is important, but not for entry level practitioners

Even as I write this, I’m imagining the hate-mail and condemnations from the people who would insist that you that you need lots of math.

So before I overstate my case, and potentially alienate a large group of people that I respect and admire, let me be clear: math is important. And in particular, there are some circumstances where math is very important.

First of all, math is particularly important if you’re doing machine learning research in an academic setting.

Second, in industry, math is also important for a small subset of more advanced data scientists. There are people in industry at high levels who are also using advanced math on a regular basis. In particular, there are people at companies like Google and Facebook who are pushing the boundaries of machine learning – people working on bleeding edge tools. These people almost certainly employ calculus, linear algebra, and more advanced math routinely in their work.

But in this article, I’m not talking about senior level data scientists working on cutting edge tools. And I’m not talking about academic work (as much as I admire academics and theorists for developing the techniques that we use on a daily basis).

I’m talking about entry level data scientists. I’m talking about people who are just getting started and trying to find a path at the very beginning stages.

Beginners do need some math for machine learning

I’ll also clarify and say that even for the beginners that I’m addressing in this article, you do need some math.

I’ll write my full advice in another blog post, but I’ll briefly summarize it here: to get started learning practical machine learning, an entry level data scientist needs to have basic comfort working with numbers, calculating percentages, etc. You need at least as much math skill as a college freshman at a good university. You’ll also need knowledge of basic statistics … about as much knowledge as you’d get in a basic “Introduction to Statistics” course. That is, you need to understand concepts like mean, standard deviation, variance, and other things you’d learn in an intro stats class.

However, when people tell you that you absolutely need to know calculus, differential equations, optimization theory, linear algebra, and more just to get started building machine learning models, this is flat out wrong.

Your first milestone: master data analysis

What does this mean for you, the beginning data scientist?

The take-away here is that for beginning data scientists and ML practitioners, data expertise beats math expertise. You’ll get much farther if you really know your way around a dataset, than if you know calculus and college-level math.

So if your goal is to get a job in business or industry, your first milestone is mastering data analysis.

It’s not mastering calculus.

It’s not being able to write proofs or grind through math problems.

It’s data analysis.

You need to master how to gather data, explore it, and prepare it. This means that you need to master data visualization and data wrangling (including aggregation). Then you need to be able to use data visualization and data wrangling together to be able to perform exploratory data analysis.

If you’re working in R, then I recommend that you learn the following:
– ggplot2 for data visualization, including basic visualizations like scatterplots, histograms, bar charts
dplyr for aggregating and reshaping a dataset
– Learn how to use ggplot and dplyr together for exploratory data analysis

If you’re working in Python, learn the following:
– Base python
– Pandas, for aggregating and reshaping your data
– Matplotlib for data visualization. In particular, learn pyplot for basic visualizations, and use Seaborn for more advanced statistical graphics
– Learn to use Pandas and data visualizations together for exploratory data analysis.

If you’re a beginner, and you want to get started with machine learning, you can get by without knowing calculus and linear algebra, but you absolutely can’t get by without data analysis.

If you master data analysis, you’ll be well prepared to start building machine learning models that work.

The post The real prerequisite for machine learning isn’t math, it’s data analysis appeared first on SHARP SIGHT LABS.

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