Data Input and Output

Question 1

What are the most basic ways to input data into R?

Answer 1

The most basic functions for data input in R are the following:
c( )
rep( )
seq( ) or :

With these basic functions, we can create objects of more specific classes like:

matrix( )
list( )
data.frame( )

Question 2

What’s the basic function to input data from keyboard into a vector?

Answer 2

scan( )

Question 3

How can I read character data from keyboard into vector x?

Answer 3

x = scan(what = “character”)

Question 4

How can I read the full name of the user from keyboard into a variable called name?

Answer 4

name = readLines(n = 1)

Question 5

How can I import a csv called “crabs.csv” into a data frame called df, using the two most common ways?

Answer 5

df = read.table(“crabs.csv”, header = TRUE)

or using wrapper function read.csv:

df = read.csv(“crabs.csv”)

Question 6

Once I’ve loaded my data frame called df, now I want to quickly see the basic structure of the dataframe and its first rows of data, what functions should I use?

Answer 6

str( df )

and

head( df )

Question 7

Can I use functions read.table and read.csv to read a csv file from a web url?

Answer 7

Yes, I just need to provide the full url to the file argument.

Question 8

How do I list the data sets available with R installation and how can I load one of them?

Answer 8

data( ) - to list

data( mtcars ) - to load data set mtcards

Question 9

How can I export my data frame Titanic to a csv?

Answer 9

write.table(Titanic, “titanic.csv”, row.names=F, sep=”,”, dec=”.”)

Question 10

What function should I use to save a file with text representation of an R object?

Answer 10

dput(da) - to output in the console

dput(da, file = “da.R”) - to write a file

Question 11

How can I write text representations of three R objects called ma, da, vec into a file? How can I load them into R later?

Answer 11

Write:

dump(c(“ma”, “da”, “vec”), file = “data.R”)

Read:
source(“data.R”)

It creates the objects in your working area with the same names and attributes with which they’ve been stored.

Question 12

What are this function calls doing? Why is it useful.

save(da, file = “dados.rda”)

save(da, ma, file = “dados.rda”)

save.image(file = “workspace.RData”)

load(“dados.rda”) l

load(“workspace.RData”)

Answer 12

Saving and loading data in binary format. It’s useful when I only have this option or when I need an absolutely great precision to store numbers.

Question 13

How can I see a list of files present in my working directory?

Answer 13

dir( )

Question 14

How can I see information about a file called “word_count.ipynb”? What kinds of information does it return?

Answer 14

file.info(“word_counter.ipynb”)

Question 15

How can I check if file word_cloud.txt is present in the directory?

Answer 15

file.exists(“word_cloud.txt”)

Returns TRUE or FALSE