4. Data Import and Export

In r02pro: R Programming: Zero to Pro

library(learnr)
library(readr)
knitr::opts_chunk$set(echo = FALSE)

4.1 Exporting Data to Delimited Files

1. If we have a data frame named my_data in R, write R code to write the data frame into a .csv file named "my_data_no_name.csv" without column names.

1. If we have a data frame named my_data in R which contains NA values, write R code to write the data frame into a delimited file called "my_data_na.csv" with # as the delimiter and use 999 as the indicator for missing values.

4.2 Importing Data from Delimited Files

1. If we have a delimited file named "my_data.txt" with * as the delimiter and the file is located in the current working directory. Write R code to read the file into an object with name my_data.

1. First, run the code below.

d1 <- read_csv("x,y,z
          1,3,5
          2,4,6", col_names = FALSE)

Which of the following are the column names of the d1?

• X1, X2, and X3

• x, y, and z

• First, run the code below.

read_csv("The first line 
          The second line
          The third line
          x,y,z
          1,3,5", )

Which of the following are the column names of the d1?

1. Which of the following is a valid object name in R?

2. 2.True

3. else
4. I_am_not_a_valid_name

5. I_am_a_Pretty#_name

6. Write R code to get the list of all objects in the environment.

2.2 Numeric Vector, Character Vector, & Logical Vector

1. Write R code to create a numeric vector named vec_1 with values (7, 24, 8, 26), get its length, and find out its type.

1. Write R code to create a character vector named char_1 with values ("I", "am", "learning", "R!"), get its length, find out its type, and concatenate the vector into a single string with space as the separator.

1. For the char_1 defined in Q2, find the number of characters in each string, and convert each string to upper case.

1. Create a length-2 logical vector representing whether vec_1 and char_1 are of character type.

1. Let class1 <- c(7, TRUE). Which of the following is the class of class1?

2. numeric

3. logical

4. character

5. Let class2 <- c(7, TRUE, "char"). Which of the following is the class of class2?

6. numeric

7. logical
8. character

2.3 Create Vectors with Patterns

1. Write R code to create consecutive integers from -10 to 10.

1. Write R code to create a decreasing sequence from 5 to 1 with increment -0.5.

1. Write R code to create an equally-spaced sequence from 2 to 6 with length 10.

1. Write R code using rep() function to create the string

c("sheep","pig", "cat","sheep","pig", "cat","sheep","pig", "cat")

1. Write R code using rep() function to create the string

c("sheep","sheep","pig","pig","pig","pig","cat","cat","cat")

r02pro documentation built on May 31, 2023, 8:09 p.m.