# Standard error

#### learnings and projects in data science

My name is Jodie Burchell and I'm a data scientist living in the beautiful city of Berlin, Germany. This blog is a collection of my projects and things I've learned using Python, R, SQL and other tools. The opinions expressed here are my own and do not reflect on my employer.

## Reading S3 data into a Spark DataFrame using Sagemaker

I recently finished Jose Portilla’s excellent Udemy course on PySpark, and of course I wanted to try out some things I learned in the course. I have been transitioning over to AWS Sagemaker for a lot of my work, but I haven’t tried using it with PySpark yet …

## Simplifying the normal equation with Gram-Schmidt

In the last post I talked about how to find the coefficients that give us the line of best fit for a OLS regression problem using the normal solution. The core of this approach is the equation:

$$X^TXb = X^Ty$$

The way we solved this in the previous post …

## Solving OLS regression with linear algebra

When I first learned least-squares linear regression in my undergrad degree, I remember that we approached it in the “calculus” way: taking the sum of the squared differences for each observation and solving a massive (and tedious) equation until we arrived at our coefficients and line of best fit. I …

## Working with matrices: powers and transposition

Today, we’ll complete our series on basic matrix operations by covering powers of a matrix and matrix transposition. In the previous posts, we covered matrix addition, subtraction and multiplication and matrix inversion.

## Powers of a matrix

Say we have a number $$a$$, and we’re asked to solve \(a …

## Working with matrices: inversion

Today we will continue our discussion of the basic operations you can do with matrices in linear algebra. In the last post we covered addition, subtraction, scalar multiplication and matrix multiplication. This week, we’ll cover matrix inversion.

So far we’ve seen matrix addition, subtraction and multiplication, but what …