You can use the following methods to count the number of TRUE values in a logical vector in R:

Method 1: Use sum()

sum(x, na.rm=TRUE)

This method will return the count of TRUE values in a vector.

Method 2: Use summary()

summary(x)

This method will return the count of TRUE, FALSE, and NA values in a vector.

The following examples show how to use each method in practice.

Example 1: Count TRUE Values Using sum()

The following code shows how to use sum() to count the number of TRUE values in a logical vector:

#create logical vector
x <- c(TRUE, FALSE, FALSE, TRUE, FALSE, FALSE, NA, TRUE)

#count TRUE values in vector
sum(x, na.rm=TRUE)

[1] 3

From the output we can see that there are 3 TRUE values in the vector.

Note: If there are NA values in the vector and we don’t use the argument na.rm=TRUE, then the function will return NA.

Example 2: Count TRUE Values Using summary()

The following code shows how to use summary() to count the number of TRUE, FALSE, and NA values in a logical vector:

#create logical vector
x <- c(TRUE, FALSE, FALSE, TRUE, FALSE, FALSE, NA, TRUE)

#count TRUE, FALSE, and NA values in vector
summary(x)

   Mode   FALSE    TRUE    NA's 
logical       4       3       1 

From the output we can see:

• There are 4 FALSE values in the vector.
• There are 3 TRUE values in the vector.
• There is 1 NA value in the vector.

The summary() function is particularly useful if you’d like to know the occurrence of each type of value in a logical vector.

If you’d like to only return the number of TRUE values from the summary() function, you can use the following syntax:

#create logical vector
x <- c(TRUE, FALSE, FALSE, TRUE, FALSE, FALSE, NA, TRUE)

#count TRUE values in vector
summary(x)['TRUE']

TRUE 
   3

From the output we can see that there are 3 TRUE values in the vector.