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.
## Rows: 3 Columns: 3
## ── Column specification ────────────────────────────────────────────────────────
## Delimiter: ","
## chr (3): X1, X2, X3
## 
## ℹ Use `spec()` to retrieve the full column specification for this data.
## ℹ Specify the column types or set `show_col_types = FALSE` to quiet this message.

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

  • X1, X2, and X3
  • x, y, and z
  1. First, run the code below.
## Warning: One or more parsing issues, see `problems()` for details
## Rows: 4 Columns: 1
## ── Column specification ────────────────────────────────────────────────────────
## Delimiter: ","
## chr (1): The first line
## 
## ℹ Use `spec()` to retrieve the full column specification for this data.
## ℹ Specify the column types or set `show_col_types = FALSE` to quiet this message.

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

  1. Which of the following is a valid object name in R?
  • 2.True
  • else
  • I_am_not_a_valid_name
  • I_am_a_Pretty#_name
  1. 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?
  • numeric
  • logical
  • character
  1. Let class2 <- c(7, TRUE, "char"). Which of the following is the class of class2?
  • numeric
  • logical
  • 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")