Write a R program to count the number of NA values in a data frame column

exam_data = data.frame(
name = c('Anastasia', 'Dima', 'Katherine', 'James', 'Emily', 'Michael', 'Matthew', 'Laura', 'Kevin', 'Jonas'),
score = c(12.5, 9, 16.5, 12, 9, 20, 14.5, 13.5, 8, 19),
attempts = c(1, NA, 2, NA, 2, NA, 1, NA, 2, 1),
qualify = c('yes', 'no', 'yes', 'no', 'no', 'yes', 'yes', 'no', 'no', 'yes')
)
print("Original dataframe:")
print(exam_data)
print("The number of NA values in attempts column:")
print(sum(is.na(exam_data$attempts)))

Sample Output:

[1] "Original dataframe:"
        name score attempts qualify
1  Anastasia  12.5        1     yes
2       Dima   9.0       NA      no
3  Katherine  16.5        2     yes
4      James  12.0       NA      no
5      Emily   9.0        2      no
6    Michael  20.0       NA     yes
7    Matthew  14.5        1     yes
8      Laura  13.5       NA      no
9      Kevin   8.0        2      no
10     Jonas  19.0        1     yes
[1] "The number of NA values in attempts column:"
[1] 4