GEOG413/613 Lab 1

R is a programming language that is widely used in areas of scientific activity and quantitative research. 

•         It is open source
•         It works on all platforms 
•         It has extensive functionality

The extensive functionally is through R packages, which are referred to as Libraries when installed. These libraries extend the core R packages. 

The Basics

You can type commands directly in the R console but you are strongly encouraged to always work with a script.

• Create a new script:
  • File -> New

• Save right away and often (this just good practice)

Basic Arithmetic

Type the following in your script

2 + 3
6 - 3
9 / 3
11 * 3
12^3

• • Try the following:
    • Press Control+Enter when the cursor on one of the lines
    • Select a few lines and then press Control+Enter
    • Select all the lines and then press Control+Enter
      • Repeat the steps above using the Run button at the top of the script window

Variable Assignment

It is convenient and helpful to assign values to variables. The form is: variable <- value

x <- 3
y <- 6
x - y 
z <- y + x 
sqrt(z)

Try: Before doing anything else, put your cursor at the of the the third line and press Control + Enter. You will probably get an error, it is important to note that the code is executed sequentially.

The basic assignment type in R is to a vector of values. A vector can be a single value shown with x, y, z above or multiple values.

heights <- c(12.2, 15.6, 16.2, 18.3,  11.5, 14.3)
heights
heights**2
sum(heights)
mean(heights)

c instructs R to concatenate multiple values.

Try to find the squareroots of the heights; the first element; elements 3, 2, and 4; elements 2 to 5, the maximum value.

• An exercise to try:
  • Create a vector bccities of the following cities in BC: Prince George, Quesnel, Chilliwack, Vancouver, Kelowna
  • Create a vector bcinterior with logical values: TRUE, TRUE, FALSE, FALSE, TRUE
  • Now use bcinterior to find a subset of bccities

Matrices

The function matrix create a matrix from the data and parameters pass to it. This must include parameters for the number of columns and rows. The function as.matrix attempts to turn (coarse) its arguments into a matrix and is.matrix tests to see whether an argument is a matrix.

matrix(ncol = 2, nrow = 0)

matrix(1:6)

matrix(1:6, ncol = 2)

matrix(1:6, nrow = 2)

as.matrix(6:3)

is.matrix(as.matrix(6:3))

Matrix rows and columns can be named.

cities.popn <- matrix(c(75150, 72406, 70981, 71974, 74003, 76708, 8468, 10044, 9326, 10007, 9879, 9889, 60186, 69217, 62927, 77936, 83788, 93203, 514008, 545671, 578041, 603502, 631486, 662248, 89442, 96288, 106707, 117312, 127380, 144576), c(5, 6), byrow = TRUE)
colnames(cities.popn) <- c("1996", "2001", "2006", "2011", "2016", "2021")
rownames(cities.popn) <- c("Prince George", "Quesnel", "Chilliwack", "Vancouver", "Kelowna")
# examine the matrix
cities.popn

Try these functions: rowSums, colSums, colMeans, rowMeans, sum, diag

• apply (x,1,max) #apply a function over rows (1) or columns(2) of x
• x[, c(TRUE,FALSE)] # logical operations to select matrix elements

Exercise:

• Lets create a 2×2 identity matrix and find its inverse.

Additional Notes