Some useful things…

Important functionality

Loading files using source(...)
Vectors, c(), seq(), head() and tail()
for loops:

    for (...) { ... }

functions:

    my_fun <- function() { ... }

if statements

    if (...) { ... } else { ... }

Using curly brackets { ... }
(joining) data frames

    data.frame(...)
    rbind(df1, df2)

Loading files

    source("0105-step-birth-death.R")
    step_deterministic_birth_death

function (latest, birth.rate, death.rate) 
{
    new.births <- birth.rate * latest$count
    new.deaths <- death.rate * latest$count
    next.count <- latest$count + new.births - new.deaths
    data.frame(count = next.count)
}

Vectors

c("Hello", "Goodbye")

[1] "Hello"   "Goodbye"

words <- c("Welcome", "Farewell")
words[2]

[1] "Farewell"

`seq()`

seq(2, 4)

[1] 2 3 4

wholes <- seq(from = 3, to = 6)
wholes

[1] 3 4 5 6

halves <- seq(from = 3, to = 7, by = 0.5)
halves

[1] 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0

`head()` and `tail()`

head(halves)

[1] 3.0 3.5 4.0 4.5 5.0 5.5

tail(halves, 1)

[1] 7

`for (...)` loops

for (item in vector) {
  do something, probably to item
}

Remember, wholes was seq(from = 3, to = 6):

for (whole in wholes) {
  print(whole)
}

[1] 3
[1] 4
[1] 5
[1] 6

`for (...)` loops

halves <- seq(from = 0, to = 1, by = 0.5)
total <- 0
for (half in halves) {
  print(half)
  total <- total + half
}

[1] 0
[1] 0.5
[1] 1

total

[1] 1.5

Functions

add_up <- function(first, second) {
  first + second
}
add_up(3, 5)

[1] 8

Functions

add_up <- function(first, second) {
  result <- first + second
}
add_up(3, 5)

Functions

add_up <- function(first, second) {
  result <- first + second
  result
}
add_up(3, 5)

[1] 8

Functions

### <b>
add_up <- function(first, second) {
### </b>
  result <- first + second
### <b>
  second - first
}
add_up(3, 5) ### </b>

[1] 2

Functions

add_up <- function(first, second) {
  # Calculate the result
  result <- first + second
  # And return it
### <b>
  result
### </b>
}
add_up(3, 5)

[1] 8

Functions

We want to calculate: \[(first + second) \times (first + second)\]

add_and_square <- function(first, second) {
  # Calculate the result
  added <- first + second
  squared <- added * added
  # And return it
  squared
}
add_and_square(3, 5)

[1] 64

Functions

Doing it all in one go increases the risk of mistakes:

add_and_square <- function(first, second) {
  (first + second) * first + second
}
add_and_square(3, 5)

[1] 29

`if (...) {...}` statements

If statements allow us to do different things depending on what has gone before in the code.

`if (...) {...}` statements

if (add_and_square(3, 5) == 64) {
  print("Maths still works")
}

`if (...) {...} else {...}`

if (add_and_square(3, 5) == 64) {
  print("Maths still works")
} else {
  warning("We have a problem")
  print(add_and_square(3, 5))
}

Warning: We have a problem

[1] 29

`if (...) {...} else {...}`

add_and_square <- function(first, second) {
  # Calculate the result
  added <- first + second
  squared <- added * added
  # And return it
  squared
}

`if (...) {...} else {...}`

if (add_and_square(3, 5) == 64) {
  usethis::ui_done("Maths still works")
} else {
  usethis::ui_oops("We have a problem")
}

✔ Maths still works

Using curly brackets `{ ... }`

Curly brackets allow us to do lots of things all in one go. You’ve seen them in for loops, if statements, function definitions. They turn multiple R statements into one block, like a code block in RMarkdown but in regular R. Make sure you don’t forget them.

Using curly brackets `{ ... }`

add_and_square <- function(first, second)
  added <- first + second
  squared <- added * added
  squared

[1] 0

add_and_square(3, 5)

Using curly brackets `{ ... }`

added <- 0
add_and_square <- function(first, second)
  added <- first + second

squared <- added * added
squared

[1] 0

add_and_square(3, 5)

Using curly brackets `{ ... }`

added <- 0
add_and_square <- function(first, second) {
  added <- first + second
}
squared <- added * added
squared

[1] 0

add_and_square(3, 5)

Using curly brackets `{ ... }`

added <- 0
add_and_square <- function(first, second) {
  added <- first + second
  squared <- added * added
  squared
}
add_and_square(3, 5)

[1] 64

Using curly brackets `{ ... }`

Notice that they actually interfere with RMarkdown

#' ## Adding a header here works!
added <- 0
add_and_square <- function(first, second) {
  #' ## Adding a header here doesn't work :(
  added <- first + second
  squared <- added * added
  squared
}

(joining) data frames

first <- head(airquality)
first

  Ozone Solar.R Wind Temp Month Day
1    41     190  7.4   67     5   1
2    36     118  8.0   72     5   2
3    12     149 12.6   74     5   3
4    18     313 11.5   62     5   4
5    NA      NA 14.3   56     5   5
6    28      NA 14.9   66     5   6

class(first)

[1] "data.frame"

last <- tail(airquality, 1)
last

    Ozone Solar.R Wind Temp Month Day
153    20     223 11.5   68     9  30

(joining) data frames

full <- rbind(first, last)
full

    Ozone Solar.R Wind Temp Month Day
1      41     190  7.4   67     5   1
2      36     118  8.0   72     5   2
3      12     149 12.6   74     5   3
4      18     313 11.5   62     5   4
5      NA      NA 14.3   56     5   5
6      28      NA 14.9   66     5   6
153    20     223 11.5   68     9  30

nrow(full)

[1] 7

Final comments

rm(list=ls())

This clears the environment, but so does generating a report, and rm() can accidentally delete useful things if it’s used in the wrong place, so never use it. If you have to clear the environment, you can clear the environment manually using Session->Clear Workspace, the brush in the Environment tab, or even better use Session->Restart R to restart everything. Next:

setwd("c/d") # and more importantly
setwd("c:\a\b\c\d")

This will set the working directory to a fixed place, which is very annoying if you ever move your code or more importantly if someone else tries to use it. Much better to use a Project, so please never put setwd() into your code anywhere.

Final comments

And finally:

install.packages("tibble")
devtools::install_github("SBOHVM/RPiR")

This should be done before you run your code (and later we’ll show you how to make sure it is done as your code is downloaded), but your scripts should not try to install packages themselves. It’s enough that loading the library will fail if the code is run. It’s obvious what to do next if that happens.

More Programming in R

Some useful things…

Important functionality

Loading files

Vectors

seq()

head() and tail()

for (...) loops

for (...) loops

Functions

Functions

Functions

Functions

Functions

Functions

Functions

if (...) {...} statements

if (...) {...} statements

if (...) {...} else {...}

if (...) {...} else {...}

if (...) {...} else {...}

Using curly brackets { ... }

Using curly brackets { ... }

Using curly brackets { ... }

Using curly brackets { ... }

Using curly brackets { ... }

Using curly brackets { ... }

(joining) data frames

(joining) data frames

Final comments

Final comments

`seq()`

`head()` and `tail()`

`for (...)` loops

`for (...)` loops

`if (...) {...}` statements

`if (...) {...}` statements

`if (...) {...} else {...}`

`if (...) {...} else {...}`

`if (...) {...} else {...}`

Using curly brackets `{ ... }`

Using curly brackets `{ ... }`

Using curly brackets `{ ... }`

Using curly brackets `{ ... }`

Using curly brackets `{ ... }`

Using curly brackets `{ ... }`