How to find position of missing values in a vector

Question

What features does the R language have to find missing values in dataframe or at least, how to know that the dataframe has missing values?

Answer 1

x = matrix(rep(c(NA, 1,NA), 3), ncol=3, nrow=3)
print(x)
     [,1] [,2] [,3]
[1,]   NA   NA   NA
[2,]    1    1    1
[3,]   NA   NA   NA

matrix of boolean values: is the value NA

is.na(x)
      [,1]  [,2]  [,3]
[1,]  TRUE  TRUE  TRUE
[2,] FALSE FALSE FALSE
[3,]  TRUE  TRUE  TRUE

indices of NA values:

which(is.na(x), arr.ind = T)
     row col
[1,]   1   1
[2,]   3   1
[3,]   1   2
[4,]   3   2
[5,]   1   3
[6,]   3   3

see if the matrix has any missing values:

any(is.na(x))
TRUE