是否有数据类型“十进制"?在R中? [英] Is there a datatype "Decimal" in R?

问题描述

我从MySQL表读取以DECIMAL格式存储的数据.我想对R中的这些数字进行计算.

I read data stored in the format DECIMAL from a MySQL-Table. I want to do calculations on those numbers within R.

我曾经使用as.numeric()将它们转换为数字表示形式，但是文档中说:

I used to cast them to a numeri represaentation using as.numeric(), but the documentation says:

数字等于双精度(实数).

numeric is identical to double (and real).

但是R中是否还有数据类型Decimal? (没有舍入错误的数据类型，...)

But is there also a datatype Decimal in R? (Datatype without rounding errors,...)

这里是一个简单的示例，说明存在舍入错误的问题:

Here a simple example for the problem with rounding errors:

numbersStrings = c("0.1", "0.9")
numbersNumeric = as.numeric(numbersStrings)
numbersMirror  = c(numbersNumeric, 1-numbersNumeric)

str(numbersMirror)

numbersMirror
unique(numbersMirror)  # has two times 0.1 ...

sprintf("%.25f", numbersMirror)
sprintf("%.25f", unique(numbersMirror))  # ... because there was a rounding error

推荐答案

您可以创建自己的:

d <- structure( list(i=589L,exp=2L), class="decimal" )
print.decimal <- function( x, ...) print( x$i * 10^(-x$exp) )
> d
[1] 5.89

实际上，某些大型软件包也可能适用于此，因为它们使用类似的表示方式....

Actually, some of the big number packages may work for this as well, since they use a similar representation....

这篇关于是否有数据类型“十进制"?在R中?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！