Republic of Mathematics blog

So you want to be a data scientist?

Posted by: Gary Ernest Davis on: May 6, 2012

Well, listen up.

Here are some a well known data scientists:

What do you need to know, and know how to do to be a data scientist, and hang with these cool folks?

First, you need to be able to hack and scrub data – lots and lots of data, usually messy.  To do this you’ll need to be familiar with a language such as Perl or Python, and keep an eye on the Julia language.

You should know how to work in the command line, in a Unix environment, to interact with APIs.

You need to know how to do a decent statistical analysis of data (again lots and lots of it). You should at least know how to carry out an exploratory data analysis, a regression (maybe even a loess regression) and design an experiment to test a hypothesis.

As part of your statistical background you should be fluent in R, and be up to speed with Python pandas.

You should know how to design and test algorithms, and be familiar with data mining and machine learning.

Database programming, of the SQL variety, should be your bread and butter.

Then you need to be very familiar with techniques of data visualization.

It would help if you knew how to carry out a simulation, and also knew something about Hadoop and Map Reduce, or – nowadays, High Performance Computer Cluster management.

If all that isn’t enough you need to be able to communicate a story really well.

If you lack some or all of these skills, you need to get up to speed by yourself or find someone, somewhere, to teach you.

This sounds like a lot, and it is – yet the work of a data scientist, is so interesting, so rewarding, and so important, that you’ll figure out how to do it.

Here’s links to the data scientists, above:

 

 

 

 

 

 

 

 

 

 

 

Why is -3+5=5-3?

Posted by: Gary Ernest Davis on: May 6, 2012

@MrMathsTeacher tweeted (5/6/2012) “Is 5x-3=7 easy, but -3+5x=7 hard due to the way neg numbers have been taught or because of algebra difficulties, or something else?”
@ColleenYoung responded:  “I think so many are not really familiar with the fact that say -3+5 is the same as 5-3. #mathchat
A lot of the difficulty for kids in learning mathematics, is knowing what models to use to think about things.
For example, in thinking about functions it helps to have a model of a function as a machine with an input and an output:
This may not be strictly correct from a rigorous point of view, yet it serves as a model that is accurate, that can be later modified as students require more rigor, and does not need to be thrown overboard to do that. It is an instance of a cognitive root.
A useful cognitive root for signed numbers, such as -3 and 5, is as instructions to move from a given place on the number line.
For example, if we imagine ourselves as being at 0 on the number line, then the number -2 instructs us to move 2 places to the left:
If we are at the point 1 on the number line the number -2 still instructs us to move 2 places to the left – it just lands as at a different spot:
Similarly, a positive number such as 4 tells us to move 4 places to the right from where we are:
Now a number such as 3 has an ambiguity of interpretation: does it mean the place 3 to the right of 0 on the number line, or does it mean to move 3 places right from where we are?
The answer, of course, depends on the context. For a number to mean a place on the number line we move that many spots from 0 (left for negative numbers, right for positive numbers). Otherwise, we keep the interpretation of a number open, as meaning move to the left or right of where we currently are on the number line.
Now with addition interpreted as following on (concatenation) we have our cognitive root of signed number addition:
-3 + 5 means move 3 places to the left of where we are and then 5 places to the right. This lands us 2 places to the right of where we started.
On the other hand, 5-3 means move 5 places to the right of where we are and then move 3 places to the left. This again lands us 2 places to the right of where we started.
In both cases, if we started at 0, then we would end at 2.
So -3+5= 2 = 5-3
At least, that’s one way to think about it.