R for Data ScienceChapter 2

Workflow Basics

Coding Basics

# you can use R for calculations
1/200*30

[1] 0.15

(59+73+2)/3

[1] 44.66667

sin(pi/2)

[1] 1

# You can create new objects with the <-
# format: object <- value
# Reads as object name gets value 
# you can use ALT and minus(-) to create tehe <-
x<- 3*4
y <- 4*5
x

[1] 12

y

[1] 20

What’s in a Name

Object names must start with a letter
It can contain numbers, letters, _, and .

this_is_really_a_long_name <- 2.5
this

Calling Functions

R functions are called like this:
function_name(arg1 = val1, arg2=val2, …)

seq(1,10)

 [1]  1  2  3  4  5  6  7  8  9 10

Quotation marks comes in pairs. If you forget the closing mark, R will tell you with [+]

y <- seq(1,10, length.out = 5)
y

[1]  1.00  3.25  5.50  7.75 10.00

Exercises

1. Why does this code not work ?
   my_variable <- 10 my-varIable # Error in eval(expr, envir, enclose): #> object “my varIable’ not found)

2. Tweak each of the following R commands so that they run correctly:

library(tidyverse)
ggplot(dota=mpg)+
  geom_point(mapping = aes(x=displ, y=hwy))

Error in structure(list(data = data, layers = list(), scales = scales_list(),  : 
  argument "data" is missing, with no default

library(tidyverse)
ggplot(data=filter(mpg, cyl==8))+
  geom_point(mapping = aes(x=displ, y=hwy))

3. Press Alt-Shift-k. What happens? How can you get to the same place using the menus?

Answer: Pops up the keyboard shortcut help!