Missing values

December 14, 2015
By

(This article was first published on R-exercises, and kindly contributed to R-bloggers)

missing valuesToday we’re training how to handle missing values in a data set. Before starting the exercises, please first read section 2.5 of An Introduction to R.

Solutions are available here.

Exercise 1
If X <- c (22,3,7,NA,NA,67) what will be the output for the R statement length(X)

Exercise 2
If X = c(NA,3,14,NA,33,17,NA,41) write some R code that will remove all occurrences of NA in X.
a. X[!is.na(X)]
b. X[is.na(X)]
c. X[X==NA]= 0

Exercise 3
If Y = c(1,3,12,NA,33,7,NA,21) what R statement will replace all occurrences of NA with 11?
a. Y[Y==NA]= 11
b. Y[is.na(Y)]= 11
c. Y[Y==11] = NA

Exercise 4
If X = c(34,33,65,37,89,NA,43,NA,11,NA,23,NA) then what will count the number of occurrences of NA in X?
a. sum(X==NA)
b. sum(X == NA, is.na(X))
c. sum(is.na(X))

Exercise 5
Consider the following vector W <- c (11, 3, 5, NA, 6)
Write some R code that will return TRUE for value of W missing in the vector.

Exercise 6
Load ‘Orange’ dataset from R using the command data(Orange) . Replace all values of age=118 to NA.

Exercise 7
Consider the following vector A <- c (33, 21, 12, NA, 7, 8) .
Write some R code that will calculate the mean of A without the missing value.

Exercise 8
Let:
c1 <- c(1,2,3,NA) ;
c2 <- c(2,4,6,89) ;
c3 <- c(45,NA,66,101) .
If X <- rbind (c1,c2,c3, deparse.level=1) , write a code that will display all rows with missing values.

Exercise 9
Consider the following data obtained from df <- data.frame (Name = c(NA, “Joseph”, “Martin”, NA, “Andrea”), Sales = c(15, 18, 21, 56, 60), Price = c(34, 52, 21, 44, 20), stringsAsFactors = FALSE)
Write some R code that will return a data frame which removes all rows with NA values in Name column

Exercise 10
Consider the following data obtained from df <- data.frame(Name = c(NA, “Joseph”, “Martin”, NA, “Andrea”), Sales = c(15, 18, 21, NA, 60), Price = c(34, 52, 33, 44, NA), stringsAsFactors = FALSE)
Write some R code that will remove all rows with NA values and give the following output

Name Sales Price
2 Joseph 18 52
3 Martin 21 33

To leave a comment for the author, please follow the link and comment on their blog: R-exercises.

R-bloggers.com offers daily e-mail updates about R news and tutorials on topics such as: Data science, Big Data, R jobs, visualization (ggplot2, Boxplots, maps, animation), programming (RStudio, Sweave, LaTeX, SQL, Eclipse, git, hadoop, Web Scraping) statistics (regression, PCA, time series, trading) and more...



If you got this far, why not subscribe for updates from the site? Choose your flavor: e-mail, twitter, RSS, or facebook...

Comments are closed.

Sponsors

Never miss an update!
Subscribe to R-bloggers to receive
e-mails with the latest R posts.
(You will not see this message again.)

Click here to close (This popup will not appear again)