Importing data into R

Question 1

function to load in CSV files

Answer 1

read.csv(“data.csv”, stringsAsFactors = FALSE)
data must be in your working directory, or the path must be specified. Strings as factors default is TRUE, sets strings as factors

Question 2

List the files in your working directory

Answer 2

dir()

Question 3

import tab delimited data

Answer 3

read.delim(x, sep = “/t” (space), header = TRUE)

Question 4

import any tabular data

Answer 4

read.table(x, sep = “”, header = FALSE, stringsAsFactors = TRUE, col.names = “”)

Question 5

which.min

Answer 5

returns the index of the smallest value in a vector

ex: cars[which.min(cars$MPG),] will return the value which the minimum MPG in the cars vector

Question 6

colClasses

Answer 6

an argument in the read.delim & read.table functions. Use this argument to specify the data class of the variables you are importing

ex: read.delim(x, sep = “”, colClasses = c(“character”, “logical”, “numeric”))

Question 7

Hadley’s data import package

Answer 7

readr

Question 8

read_csv()

Answer 8

readr version of read.csv
read_csv(“mydata”)
loads data as a “tibble”

Question 9

read.delim for readr

Answer 9

read_tsv (tab seperated value)(“potatoes.txt”, col_names = c(“type”, “weight”))

Question 10

col_types

Answer 10

argument to specify the variable classes in readr package

Question 11

read_delim

Answer 11

the main import function in the readr package. Similiar to read.table
Must specify the file and delim arguments
ex/ read_delim(“cars.txt”, delim = “/t”, col_names = c(“automaker”,”mpg”))

Question 12

skip

Answer 12

skip rows in your import functions.

ex: skip = 5 will skip the first 5 rows and then begin reading in data

Question 13

n_max

Answer 13

specifies the number of rows you want to read in, often used with skip

ex: read_delim(“cars.txt”, delim = “/”, skip = 2, n_max = 3)
skips the first two rows and reads in rows 3,4, and 5

Question 14

readxl

Answer 14

Haddley’s excel data import package

Question 15

function to list different sheets in excel: readxl package

Answer 15

excel_sheets()

Question 16

read_excel()

Answer 16

import excel data into R

Question 17

import data from the second sheet in an excel doc

Answer 17

read_excel(“cars.xls”, sheet = 2)

Question 18

pop_list

Answer 18

Utilize lapply with readxl functions to read in all sheets in an excel file at once. Must specify the path as a separate argument because the excel_sheets argument only lists the sheets in the file, it does not list the file path

Question 19

col_types

Answer 19

argument in read_excel. specify the data type of columns “text”, “numeric”, “date”, “blank”

Question 20

col_types = (“blank”)

Answer 20

read_excel will skip the import of a column with “blank” as col_type.
ex: read_excel(“my.data.xlsx”, col_types = c(“numeric”, “blank”)) will only import column 1 as a numeric column from the excel document

Question 21

read_excel(“data.xlsxl”, skip = 2)

Answer 21

skip the first two rows of an excel document and then begin importing data

Question 22

XLConnect

Answer 22

a package that creates a bridge between r session and excel

Question 23

XLConnct function that builds a bridge betwen R and excel

Answer 23

loadWorkbook()

Question 24

XLConnect function lists the available sheets in an excel workbook. Requires an XLConnect workbook object as first argument (created through loadWorkbook() function)

Answer 24

getSheets()

Question 25

XLConnect function loads worksheets in as data. Requires an XLConnect workbook object as first argument

Answer 25

readWorksheet()

Question 26

arguments in readWorksheet( my_book, startCol = 1, endCol = 3, starRow = 1, endRow = 3)

Answer 26

import in data from the "my_book" workbook object starting in column 1 and ending in column 3. ie only import data from column 1:3 and row 1:3

Question 27

XLConnect function to add new sheets to an excel workbook object (the bridget created through loadWorkbook())

Answer 27

createSheet( workbook object, "new_SheetName")

Question 28

add data to an XLConnect workbook

Answer 28

writeWorksheet(workbook object, new data, "sheet_to_write_to)

Question 29

save an XLConnect workbook to a new file

Answer 29

saveWorkbook(my_workbook, "filename.xlsx")

Question 30

rename a sheet using XLConnect

Answer 30

renameSheet(my_workbook, sheet = 1, newName = "cars")