Question

我正在尝试计算2 ** 1000并总结数字的值。对于所有意图和目的，似乎就像我有正确的方法，但错误的答案，我不确定是否有一种特殊的方式来做总和或者我的选项可能搞砸了。

在任何情况下，R中的2 ** 1000给出：1.072e + 301。我用了

options("scipen"=400, "digits"=4)

摆脱科学记数法（因为我们想要数字），这给了我：

10715086071862673211222842640062602864002646240220400600628246062604626466468802860684246408802204448642628020644428680866666080884644840024840004280840848880462604626804200880464480884860464420284266864402822668802420668620402620400466086288824662642224206428624064400880244462828666486484022626226666

所以我做了天真的事情并做了这些数字的总和（）

sum(1,0,7,1,5,0...)

但我得到的答案是1200，这是不正确的。我想不出sum函数如何返回一些时髦的东西，所以我假设选项搞砸了指数结果？

Answer 1

要计算 2 ** 1000 ，您必须使用BigInteger等效值，例如

http://cran.at.r-project.org/web/packages/Brobdingnag/index.html

正确答案是

2 ** 1000 =

10715086071862673209484250490600018105614048117055336074437503883703510511249361224931983788156958581275946729175531468251871452856923140435984577574698574803934567774824230985421074605062371141877954182153046474983581941267398767559165543946077062914571196477686542167660429831652624386837205668069376

数字之和为 1366

Answer 2

您可以使用gmp库来处理大整数：

library(gmp)
bigNum <- as.bigz(2)^1000
# Now we want to split into characters so we can sum the numbers:
chars <- as.integer(strsplit(as.character(bigNum), "")[[1]])
sum(chars)
# 1366

Answer 3

或者这是获得正确答案的另一种方法（诀窍是将大整数视为字符串来分割数字）：

options("scipen"=400, "digits"=4)
a <- 2^1000
a
[1] 10715086071862673209484250490600018105614048117055336074437503883703510511249361224931983788156958581275946729175531468251871452856923140435984577574698574803934567774824230985421074605062371141877954182153046474983581941267398767559165543946077062914571196477686542167660429831652624386837205668069376
b <- strsplit(as.character(a),"")[[1]]
b
  [1] "1" "0" "7" "1" "5" "0" "8" "6" "0" "7" "1" "8" "6" "2" "6" "7" "3" "2" "0" "9" "4" "8" "4" "2" "5" "0" "4" "9" "0" "6" "0" "0" "0" "1" "8" "1" "0" "5" "6" "1"
 [41] "4" "0" "4" "8" "1" "1" "7" "0" "5" "5" "3" "3" "6" "0" "7" "4" "4" "3" "7" "5" "0" "3" "8" "8" "3" "7" "0" "3" "5" "1" "0" "5" "1" "1" "2" "4" "9" "3" "6" "1"
 [81] "2" "2" "4" "9" "3" "1" "9" "8" "3" "7" "8" "8" "1" "5" "6" "9" "5" "8" "5" "8" "1" "2" "7" "5" "9" "4" "6" "7" "2" "9" "1" "7" "5" "5" "3" "1" "4" "6" "8" "2"
[121] "5" "1" "8" "7" "1" "4" "5" "2" "8" "5" "6" "9" "2" "3" "1" "4" "0" "4" "3" "5" "9" "8" "4" "5" "7" "7" "5" "7" "4" "6" "9" "8" "5" "7" "4" "8" "0" "3" "9" "3"
[161] "4" "5" "6" "7" "7" "7" "4" "8" "2" "4" "2" "3" "0" "9" "8" "5" "4" "2" "1" "0" "7" "4" "6" "0" "5" "0" "6" "2" "3" "7" "1" "1" "4" "1" "8" "7" "7" "9" "5" "4"
[201] "1" "8" "2" "1" "5" "3" "0" "4" "6" "4" "7" "4" "9" "8" "3" "5" "8" "1" "9" "4" "1" "2" "6" "7" "3" "9" "8" "7" "6" "7" "5" "5" "9" "1" "6" "5" "5" "4" "3" "9"
[241] "4" "6" "0" "7" "7" "0" "6" "2" "9" "1" "4" "5" "7" "1" "1" "9" "6" "4" "7" "7" "6" "8" "6" "5" "4" "2" "1" "6" "7" "6" "6" "0" "4" "2" "9" "8" "3" "1" "6" "5"
[281] "2" "6" "2" "4" "3" "8" "6" "8" "3" "7" "2" "0" "5" "6" "6" "8" "0" "6" "9" "3" "7" "6"
sum(as.integer(b))
[1] 1366

这适用于我的设置（即Mac OS X与R 2.14.2,32位），没有任何额外的包。还尝试了32位和64位的vanilla会话，他们都给出了1366。

R中的大国

3 个答案: