How to filter out na in R

Question

Below is the code:

library(tidyverse)
df <- tibble(
    ~col1, ~col2, ~col3,
    1, 2, 3, 
    1, NA, 3, 
    NA, 2, 3
)

I can remove all NA observations with drop_na():

df %>% drop_na()

Or remove all NA observations in a single column (col1 for example):

df %>% drop_na(col1)

Why can't I just use a regular != filter pipe?

df %>% filter(col1 != NA)

Why do we have to use a special function from tidyr to remove NAs?

Answer 1

This has nothing to do specifically with dplyr::filter. But, any comparison with NA, including NA==NA will return NA.

R does not know about what you are doing in your analysis.

So, basically it does not allow comparison operators to think NA as a value.

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Answer 2

Try this:

df %>% filter(!is.na(col1))

Comments

Thanks, that worked :)

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This was simple, direct and perfect...thank you!

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Thanks for your contribution!

In case you found the answer helpful do upvote the answer and increase your points!

Cheers!!!

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Thanks a lot!

Answer 3

Null values have no notion of equality in R. Therefore, NA == NA just returns NA. In fact, NA compared to any object in R will return NA. The filter statement in dplyr requires a boolean argument, so when it is iterating through col1, checking for inequality with filter(col1 != NA), the 'col1 != NA' command is continually throwing NA values for each row of col1. This is not a boolean, so the filter command does not evaluate properly.

Comments

Thanks Zane! That was very well explained.

Answer 4

Can we create a alist as below to find the rows which has no null values and then provide the list to dplyr function to filter rows with positions values??

Here na.omit(airquality$Ozone) will have values of not null values.

Then provide the list of positions to filter function?

Answer 5

Hi,

The dplyr has ’filter()’ function to do such filtering, but there is even more. With dplyr you can do the kind of filtering, which could be hard to perform or complicated to construct with tools like SQL and traditional BI tools, in such a simple and more intuitive way. For example, we have one flight dataset and removing NA values with the filter keyword.

flight %>%
select(FL_DATE, CARRIER, ORIGIN, ORIGIN_CITY_NAME, ORIGIN_STATE_ABR, DEP_DELAY, DEP_TIME, ARR_DELAY, ARR_TIME) %>%
filter(!is.na(ARR_DELAY))

Comments

Dear edureka.co administrator, Your posts are always well written.