## Data Structures in R

Before I learned R, I had previously only programmed in Matlab. Matlab and R have comparable options for data types and treat objects very similarly, but R, and specifically the Tidyverse, has this whole other vocabulary for data structures. Understanding the differences between matrices, data frames, and other data structures made learning R easier for… Continue reading Data Structures in R

## Vocab Word: Kernel

Today's vocab word can mean a lot of things in different contexts, but it almost always means the center or core. A kernel can refer to the edible interior of a nut or seed. In computer science, a kernel is part of an operating system. On Spatially Challenged, I'm usually referring to kernel in a… Continue reading Vocab Word: Kernel

## Vocab Words: Euclidean and Cartesian

Here on Spatially Challenged, I post things people ask me about. The bigger topics (SAGA GIS, data sources, Word tricks, etc.) get turned into series of how-to posts, and the smaller questions inspired a series of vocab posts. Today we're talking about the words Euclidean and Cartesian. Euclidean means "related to Euclid." Euclid was a… Continue reading Vocab Words: Euclidean and Cartesian

## Vocab Word: Multicollinearity

I'm going to continue highlighting words I get asked about regularly. Today's feature: multicollinearity! This is a word you've probably heard about in stats class, but might not know specifically what it is or why it matters. We worry about multicollinearity when we are using multiple independent variables to model one output. One of your… Continue reading Vocab Word: Multicollinearity

## Vocab Word: Cache

There are some words I get asked about a lot, so I decided to make a running feature on my blog about them. Today's word is cache. It can be a noun or a verb, but I'm going to focus on the verb use because that's the one I get asked about. What does it… Continue reading Vocab Word: Cache

## Defining Common Terrain Derivatives

Last month I shared some ways to calculate terrain derivatives in SAGA, focusing on the Basic Terrain Analysis function. Today I'm going to give you a quick overview of what each derivative means and some of its potential uses. Let's start with the most intuitive ones. Slope is how fast elevation is changing. A higher… Continue reading Defining Common Terrain Derivatives

## What are terrain derivatives?

Lots of people have been asking me about terrain derivatives lately, and I've been putting off blogging about them for a while because I just didn't know where to start. Instead of one master post with all the things I decided to split it into some more manageable chunks-- for both your sake and mine.… Continue reading What are terrain derivatives?

## What’s a datum?

Earlier in the week I gave a quick overview of map projections. Today I'm covering a related topic--datums. North American Datum 1983 is the basis for a lot of common map projections, and World Geodetic System 1984 is the series of latitude and longitude most commonly used on consumer GPS devices. But first, what's a… Continue reading What’s a datum?

## What’s a map projection?

At the most basic level, map projections are how we turn the 3D earth surface into something flat. There are polar projections that look at the globe from the top or bottom view, or more common projections that are centered near the equator. Map projections are really easy to overlook, but have large impacts on… Continue reading What’s a map projection?

## What is a Shapefile?

Shapefiles are one of the main types of data you work with in a GIS. I have a description of GIS here, and an intro to the other basic data type (rasters) here. Shapefiles are vector data, and vector data comes in three basic forms: polygons, lines, or points. Polygons are shapes that take up… Continue reading What is a Shapefile?