编写函数来计算向量中 NA 值的数量，同时忽略指定的索引

Question

我正在尝试编写一个函数来计算向量（在第一个参数中指定）中 NA 值的数量，该函数在进行计数时也会忽略一些索引（在第二个参数中指定） .

例如，如果我有 x = c(1,NA,3,4,NA,6,NA,8,9)

我想给我们一个函数 countNA(vector = x, ignore = c(5,7)) return 计数为 1（函数被告知忽略 x[5] 和 x[7]

这是我迄今为止尝试过的方法，但它不起作用：

countNA.2 = function(x, ignore){ 
    #define a function with arguments "x" (vector to be searched for NAs) 
    #and "ignore" vector indices to be ignored if NA
    count = c() #define empty vector to hold the counts of na in vector x
    t = c(1:9) #define a reference vector to represent possible indicies
    #(max vector length is 9)
    for (q in t){ #loop through our possible vector indicies
        ifelse(q %in% ignore, count[q] = 0, count[q] = is.na(x[q])) 
        #if index is in ignore vector, then set count[q] = 0 
        #else, set count[q] = TRUE for NA and FALSE otherwise
    }
    numoccurrences = sum(count) #after we're done, sum our count vector
    return(numoccurrences) #return
}

Answer 1

只需从向量中删除值并取 is.na 的 sum:

cntNA <- function(x, ignore) sum(is.na(x[-(ignore)]))
cntNA(x, ignore=c(5,7))
#[1] 1

如果要考虑 ignore 未指定，只需添加 if/else 条件：

cntNA <- function(x, ignore=NULL) {
  if (is.null(ignore)) {
    sum(is.na(x))
  } else
  {
    sum(is.na(x[-(ignore)]))
  }
}

cntNA(x)
#[1] 3

cntNA(x, ignore=c(5,7))
#[1] 1

编写函数来计算向量中 NA 值的数量，同时忽略指定的索引

Writing function to count number of NA values in vector while ignoring specified indices

r

function

vector

na