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?
答案 0 :(得分:1)
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
和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("")
或""
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......)
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
}