r中的和NA值

Question

I am using a dataframe that has multiple NA values so I was thinking about sorting the attributes based on their NA values. I was trying to use a for loop and this is what I have so far:

> data <- read.csv("C:/Users/Nikita/Desktop/first1k.csv")
> for (i in 1:length(data) ) {
+ temp <- c(sum(is.na(data[i])))}
> temp
[1] 0

It is the first time I am using a for loop in r so I am sure it is just a silly syntax problem but I can't understand which one exactly.

Ultimately, I need a list that shows the name of the attribute and its NA count. This way I could sort the list and get the desired information. Here is some mock data to make it easier.

data <- data.frame(A = c(500, 600, 700, 1000),
                   B = c(500, 600, 700, NA),
                   C = c(NA, NA, 500, 700),
                   D = c(800, NA, 933, NA),
                   E = c(NA, NA, NA, NA))

Edit: Thank you all for the help. All three solution worked for me. I do wonder though if there is a one line code that will sort those attributes before I export them into a file. like I mentioned before, I am quite new in r so I am not sure if it is possible.

Edit 2: When I run the sort is gives me the next error:

temp <- sort(temp)
Error in sort.int(x, na.last = na.last, decreasing = decreasing, ...) : 
  'x' must be atomic

Any idea why?

Answer 1

Here is a quick answer using is.na and colSums :

colSums(is.na(data))

returning:

 A B C D E 
 0 1 2 2 4 

for your above data.

Thanks to @akrun for showing my surplus apply

Answer 2

The right way to do iterative code in R is to avoid explicit for loops. Use apply (and the company) instead. @jeremycg gave you the right R-ish answer. Regarding your code, you should make some editing to make it work.

temp <- c()
for (i in 1:length(data)){
    temp[names(data)[i]] <- sum(is.na(data[i]))
}

You had temp rewritten at each iteration. Moreover you didn't write the labels of your variables into temp . Hence the output you see is the number of NA s in the last column of your dataset.

Regarding OP's edit

temp <- sort(temp) # pass decreasing=T into arguments in case
                   # you want reversed order

Answer 3

This answer shows how to make the for loop work.

temp <- vector(length = ncol(data))

for (i in 1:length(data)) {
   temp[i] <- c(sum(is.na(data[, i])))
}

names(temp) <- colnames(data)

temp
# A B C D E 
# 0 1 2 2 4