Chapter 1
We Start Here
This book is a story about linear algebra, the main character of which is
the star of this discipline, the vector. We will start by defining this
concept, that prides itself on its simplicity. But don’t mistake simplicity
for lack of power; from an uncomplicated vector we will arrive at
complex methods like the single value decomposition and the principal
component analysis.
My journey began when I was only four years old, and my father
gave me my first book on equations. Since then, I have never looked
back. Mathematics flowed in my mind, and calculations came out as
naturally as a delicate butterfly landing on a ravishing red petal of this
miracle of nature that we so often call a flower… don’t be scared already!
We are just at the second paragraph, and this is not true. I am just a
regular guy who was most likely kicking a ball around when he was four.
But, being a typical fellow, my struggle with mathematics was real
during a specific time in my life, my first couple of years at university.
This was because of a combination of a bad attitude and a need for
content to be structured more like a story than a manual. I was scared of
equations and blamed everything I could, except myself, for my lack of
success in understanding mathematics. When I look back now, I
can see that it is impossible to understand anything with that
attitude.
Symbols and Greek letters are the alphabets of mathematics, whereas
equations are the words that represent abstract concepts. One needs to
try to understand how to read this syntax, as it will bring significant
benefits in the future. Unfortunately, mathematics has no sound, so I
don’t think you can expect good results by using a hands-on approach
where you learn by ignoring the syntax, as you might do with a musical
instrument. Still, as a mathematician, I can’t say that this way is not
possible. After all, the realm of uncertainty is where we do our
best work. Once I overcame this first hurdle and I started to be
able to read equations, another issue arose. I knew concepts in
isolation, but relating them to one another seemed impossible.
Different books have distinct structures and expose the same
ideas in varying sequences, which became another obstacle for me.
Now I say that I was lucky, but at the time, I considered myself
the unluckiest person in the world. I could not have been more
wrong.
The itinerary whereby I began putting concepts together and
understanding mathematics started on the day I missed the meeting
where we, the students, were due to meet the professors who would be
supervising our university theses. I can’t provide a good reason for
missing this meeting that won’t make you think I am an idiot, but hey,
sometimes things have a funny way of resolving themselves.
When I finally returned to the mathematics department, my
colleagues came to me with a concerned look, enquired where I had
been, and told me that I was in trouble as I had landed the worst
supervisor ever. This lady was famous for being extremely demanding
and challenging to get along with. On that same day, the path
of my life changed completely. Indeed, she was demanding, and
she presented me with a project I knew very little about, but
had to master. She made me study, and did not give anything
back to me unless she saw that I had made an effort. I had to go
back to basics, but this time I decided to start with the most
elementary concept of each subject, then I studied it in such a way that
everything moving forward would have to be the result of knowledge I
had previously acquired. This way, I could put everything into
context.
I am still a data scientist. Well, in reality, I am a mathematician. I
don’t like that job title, but I also need to pay the bills. It helps me. The
point is that my Master’s thesis was the hardest thing I have ever done,
and the conclusion is that if you make a significant effort to learn the
basics, what comes afterwards will be a smoother ride. There is a lot of
talk these days about the wealth gap, but I feel that another gap is
emerging, one in knowledge. We like to press buttons and obsess about
whatever is the next exciting thing. Modern entertainment and social
media have given us all attention deficit disorder. When this is
associated with a right-now mentality, it significantly contributes to this
problem.
If I go back to my first experience with a mathematics book, I can
understand why this might happen. With so much information out there,
the minimal hurdle presented to somebody trying to learn something
new is enough to make them try something else. There are a lot of us
pressing buttons. Still, only a few of us are building them. If you
want to succeed as a data scientist, it would be better to take a
button-builder path. What this means is that you will have to learn
mathematics.
I wrote this book aiming to help the reader to start and never have
to look or go anywhere else for further information. There will be
no need for notebooks, pens, laptops, or pencils: just the safe
blueprint, a mask, and the machine gun. Oh sorry, those last
items might have come from the “bank project” list… actually,
you won’t need much more than the Pythagorean theorem: my
mistake.