# Learn Data Science with Lekan Esan – Day 4 In my journey to learning Data Science, today, I’ve studied Permutations (P), Variations (V), and Combinations (C) which are fundamental concepts in Combinatorics. P, V and C deals with counting and arrangment of objects.

I found a very concise video that explains the concept of Permutation and Combination. It’s a 10 minutes video and it’s worth the time.

From the lessons I’ve noted some key points and formulars.

n factorial

n! = n x (n-1) x (n-2) x … x 1

Negative numbers don’t have a factorial

0! = 1

! means factorial

Permutation

n P r = n! / (n – r)!

Where n is the total number of distinct elements and r is the number of elements taken at a time.

Combination

n C r = n! / r! (n – r)!

Interesting? Yea.

I couldn’t cover much in the last two days so I didn’t write any article about my journey.

I am eager to get past the rudiments so I can start applying the knowledge to real world business problems.

I’m still learning more about the concept of Probability and the next topic on my course outline is Bayesian Inference. See you tomorrow.