为什么as.integer64("")返回0而不是NA_integer64_?

时间:2017-09-20 21:34:03

标签: r bit64

鉴于空字符串的基础as.integer()强制是NA而没有警告,如:

str( as.integer(c('1234','5678','')) ) # int [1:3] 1234 5678 NA -- no warning

我很难理解为什么bit64::as.integer64()在没有警告的情况下强迫归零:

library('bit64')
str( as.integer64(c('1234','5678','')) ) # integer64 [1:3] 1234 5678 0 -- no warning

比较更奇怪的是:

str( as.integer(c('1234','5678','', 'Help me Stack Overflow')) ) 
# int [1:4] 1234 5678 NA NA -- coercion warning

使用:

str( as.integer64(c('1234','5678','', 'Help me Stack Overflow')) ) 
# integer64 [1:4] 1234 5678 0 NA -- no warning

我的解决办法惨遭失败:

asInt64 <- function(s){
  require(bit64)
  ifelse(grepl('^\\d+$',s), as.integer64(s), NA_integer64_)
}
str(asInt64(c('1234','5678','', 'Help me Stack Overflow')) )
# num [1:4] 6.10e-321 2.81e-320 0.00 0.00
# huh?

所以,我问:

  • 为什么会这样?

  • 最佳解决方法是什么?

1 个答案:

答案 0 :(得分:1)

为什么会发生

正如@ lukeA的评论指出的那样,isVowel :: Char -> Bool isVowel c = elem c "aeiouy" vowel [] = False vowel (x:xs) = isVowel x || vowel xs 的来源是:

as.integer64.character

SEXP as_integer64_character(SEXP x_, SEXP ret_){ long long i, n = LENGTH(ret_); long long * ret = (long long *) REAL(ret_); const char * str; char * endpointer; for(i=0; i<n; i++){ str = CHAR(STRING_ELT(x_, i)); endpointer = (char *)str; // thanks to Murray Stokely 28.1.2012 ret[i] = strtoll(str, &endpointer, 10); if (*endpointer) ret[i] = NA_INTEGER64; } return ret_; } 在调用strtoll("")""等无效值时返回0并返回错误。一个引用strtoll example处理如下:

"ABCD"

所以我现在要弄清楚的是/* If the result is 0, test for an error */ if (result == 0) { /* If a conversion error occurred, display a message and exit */ if (errno == EINVAL) { printf("Conversion error occurred: %d\n", errno); exit(0); } /* If the value provided was out of range, display a warning message */ if (errno == ERANGE) printf("The value provided was out of range\n"); } 评估为FALSE的原因。 (请继续关注......)

解决方法

以下是模仿基座*endpointer行为的解决方法:

as.integer

要看到这个有效:

library(bit64)
charToInt64 <- function(s){
  stopifnot( is.character(s) )
  x <- as.integer64(s)
  # as.integer64("") unexpectedly returns zero without warning.  
  # Overwrite this result to return NA without warning, similar to base as.integer("")
  x[s==""] <- NA_integer64_
  # as.integer64("ABC") unexpectedly returns zero without warning.
  # Overwrite this result to return NA with same coercion warning as base as.integer("ABC")
  bad_strings <- grepl('\\D',s) # thanks to @lukeA for the hint
  if( any(bad_strings) ){
    warning('NAs introduced by coercion')
    x[bad_strings] <- NA_integer64_  
  }
  x
}