- 01Setting up (what you'll need)
- 02Your first output (print)
- 03Using variables
- 04Branching (the if statement)
- 05Repeating (the for loop)
- 06Writing your own function
- 07Working with vectors
- 08Repeating (the while loop)
- 09Structured data with lists
- 10Error handling (tryCatch)
- 11Sorting a vector
- 12Recursive functions
- 13Using the handy built-in functions
- 14The switch() function
- 15Applying a condition across a vector with ifelse()
- 16Applying a function across data with sapply()
- 17Writing comments
- 18Logical operators (&&, ||, !)
- 19Constants (the upper-case convention)
- 20Splitting and joining strings (strsplit and paste)
- 21Writing NULL-safe code
- 22Searching a vector (%in%)
- 23Transforming a vector with sapply (the map equivalent)
- 24Tabular data with matrices
- 25Creating your own condition
- 26Default arguments
- 27Set operations (union, intersect, setdiff)
- 28Checking correctness with stopifnot (a first step towards testing)
- 29Higher-order functions (passing a function as an argument)
- 30Stacks and queues (the basics of data structures)
- 31The basics of type conversion (casting)
- 32An introduction to regular expressions (pattern matching)
- 33The binary search algorithm
- 34Building a Caesar cipher (a letter-shifting cipher)
- 35Understanding how bubble sort works
- 36Assembling and displaying a date
- 37Writing several tests together (multiple test cases)
- 38Speeding up calculation with memoization (caching)
- 39Normalizing strings (trimws and case)
- 40Shallow copies versus deep copies
- 41factor, R's equivalent of an enum
- 42Flattening a list
- 43Reversing a string and testing for a palindrome
- 44Pairing up two vectors (the zip operation)
- 45Rounding numbers (floor, ceiling, round)
- 46Assembling multi-line text
- 47Returning several values from a function (lists)
- 48Finding the GCD and LCM (the Euclidean algorithm)
- 49Formatting numbers (aligning digits and decimal places)
- 50Cleaning up with tryCatch's finally
- 51Type-agnostic general functions
- 52The basics of reading and writing files
- 53Generating random numbers
- 54Bitwise operations (bitwAnd, bitwOr, bitwXor, shifts)
- 55Receiving command-line arguments
- 56Pausing for a set time (Sys.sleep)
- 57Watch out for floating-point error
- 58Reading a value from standard input
- 59FizzBuzz (the classic exercise)
- 60Testing whether a number is prime
- 61Set operations (union, intersection, difference)
- 62Converting between bases (binary and hexadecimal)
- 63Checking that brackets match (an application of stacks)
- 64Testing whether two words are anagrams
- 65Testing whether a year is a leap year
- 66Converting temperatures (Celsius and Fahrenheit)
- 67Finding the prime factors
- 68[Project] Build a simple inventory system
Tabular data with matrices
This lesson covers using matrix in R, with the aim of handling data in table form.
The matrix() function expresses a grid with rows and columns — a matrix. You reach into it as m[row, column].
The sample code builds two rows by three columns with matrix(c(1, 2, 3, 4, 5, 6), nrow = 2, byrow = TRUE) and reaches a value with a comma-separated row and column, as in m[2, 3]. Note byrow = TRUE, which fills the values row by row.
A common early stumble is that byrow argument. Leave it out and the values are filled column by column, giving a matrix laid out differently from what you intended.
In professional work, matrix arithmetic — statistical calculation, representing image data — is one of the areas R is strongest in.
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