Missing Values

How many missing values are in the Ozone column of this data frame?

I want to calculate the number of missing values in a column without having to count them by hand. I’m not sure how to subset only one column of data.

I try this:

ProgrammingQuizW1_data_missingvalues_completecases

It gives me 153 values. This is the number of rows in the data matrix. But, I’m not sure which columns are represented here.

I try this:

ProgrammingQuizW1_data_missingvalues_attempt

And while it seems to print all rows of just the first column and displays the number of missing values, I would have to count them by hand. I want to code a counter to do this for me. There is no mention in the Coursera lecture notes about how to count the number of occurrences. I try a Google search for “R count number of missing values in column” and this was helpful:

[1] http://forums.psy.ed.ac.uk/R/P01582/essential-10/

I try this and it seems to work:

ProgrammingQuizW1_data_missingvalues_works_sortof

The closest multiple choice option on the quiz is 43. I select this, but get the answer wrong.

Question Explanation

The `is.na’ function can be used to test for missing values.

I’ve already used this, but clearly in the wrong way. So. Let’s try again.

ProgrammingQuizW1_data_subset4

ProgrammingQuizW1_data_subset4_answer

This is the correct answer.

Advertisements

About Lisa Cohen

PhD student at UC Davis.
This entry was posted in Coursera, R. Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s