Get an output for column name and it's column number at the same time-CodePudding

I am trying to get the column name and number of columns that have "NA" in them, I have tried using this code

names(df)[sapply(df, anyNA)]

but it only gives me the column names and no the numbers, any idea how to get an output for both?

CodePudding user response：

We may convert the logical vector to index with which and subset the index with names to get the column names

i1 <- sapply(df, anyNA)
which(i1)
names(df)[i1]

We may not need the names(df)[i1] as which gives a named vector of index though i.e

which(sapply(df, anyNA))

will be a single line code to give both column names and index

Or with dplyr

library(dplyr)
df %>% 
   summarise(across(where(anyNA), ~ match(cur_column(), names(df))))

CodePudding user response：

Using which with colsums of NA.

which(colSums(is.na(iris_na)) > 0)
# Sepal.Length Petal.Length 
#            1            3

Data:

iris_na <- iris
iris_na[c(1, 3)] <- lapply(iris_na[c(1, 3)], \(x) replace(x, sample(length(x), length(x)/10), NA_real_))