zMachine(base)
zMachine()所属R语言包：base
Numerical Characteristics of the Machine
机器的数值特征
译者：生物统计家园网 机器人LoveR
描述----------Description----------
.Machine is a variable holding information on the numerical characteristics of the machine R is running on, such as the largest double or integer and the machine's precision.
.Machine是一个变量持有信息的数字特征的机R上运行，如最大的双整数和机器的精度。
用法----------Usage----------
.Machine
Details
详情----------Details----------
The algorithm is based on Cody's (1988) subroutine MACHAR. As all current implementations of R use 32-bit integers and almost all use IEC 60559 floating-point (double precision) arithmetic, all but the last two values are the same for almost all R builds.
该算法的基础上科迪（1988年）的子程序马查尔。作为当前实现所有的R使用32位整数和几乎全部采用IEC 60559浮点（双精度）的算术，但最后两个值是相同的，几乎所有的R建立。
Note that on most platforms smaller positive values than .Machine$double.xmin can occur. On a typical R platform the smallest positive double is about 5e-324.
请注意，在大多数平台上比.Machine$double.xmin较小的正面的价值观可能发生。一个典型R平台上最小的正面双约5e-324。
值----------Value----------
A list with components
与组件列表
参数：double.eps
the smallest positive floating-point number x such that 1 + x != 1. It equals double.base ^ ulp.digits if either double.base is 2 or double.rounding is 0; otherwise, it is (double.base ^ double.ulp.digits) / 2. Normally 2.220446e-16.
最小的正浮点数x1 + x != 1。它等于double.base ^ ulp.digits如果任double.base是2或double.rounding0;否则，它是(double.base ^ double.ulp.digits) / 2。通常2.220446e-16。
参数：double.neg.eps
a small positive floating-point number x such that 1 - x != 1. It equals double.base ^ double.neg.ulp.digits if double.base is 2 or double.rounding is 0; otherwise, it is (double.base ^ double.neg.ulp.digits) / 2. Normally 1.110223e-16. As double.neg.ulp.digits is bounded below by -(double.digits + 3), double.neg.eps may not be the smallest number that can alter 1 by subtraction.
一个小的正浮点数x等1 - x != 1。它等于double.base ^ double.neg.ulp.digits如果double.base是2或double.rounding0;否则，它是(double.base ^ double.neg.ulp.digits) / 2。通常1.110223e-16。 double.neg.ulp.digits范围低于-(double.digits + 3)，double.neg.eps未必是最小的数字，可以改变减法1。
参数：double.xmin
the smallest non-zero normalized floating-point number, a power of the radix, i.e., double.base ^ double.min.exp. Normally 2.225074e-308.
最小的非零规范化浮点数，基数的权力，即，double.base ^ double.min.exp。通常2.225074e-308。
参数：double.xmax
the largest normalized floating-point number. Typically, it is equal to (1 - double.neg.eps) * double.base ^ double.max.exp, but on some machines it is only the second or third largest such number, being too small by 1 or 2 units in the last digit of the significand. Normally 1.797693e+308. Note that larger unnormalized numbers can occur.
最大的规范化浮点数。通常情况下，它等于(1 - double.neg.eps) * double.base ^ double.max.exp，但在某些机器上，它仅仅是第二或第三大数目，由1个或2个单位的尾数的最后一位数字太小了。通常1.797693e+308。请注意可能会出现较大的非标准化的数字。
参数：double.base
the radix for the floating-point representation: normally 2.
基数的浮点表示：通常2。
参数：double.digits
the number of base digits in the floating-point significand: normally 53.
在浮点尾数基地的数字：通常53。
参数：double.rounding
the rounding action, one of<br> 0 if floating-point addition chops; <br> 1 if floating-point addition rounds, but not in the IEEE style; <br> 2 if floating-point addition rounds in the IEEE style; <br> 3 if floating-point addition chops, and there is partial underflow; <br> 4 if floating-point addition rounds, but not in the IEEE style, and there is partial underflow; <br> 5 if floating-point addition rounds in the IEEE style, and there is partial underflow.<br> Normally 5.
四舍五入行动，参考0，如果浮点加法如果浮点加法弹，但没有在IEEE样式印章;参考1参考2，如果在IEEE风格浮点加法发;参考3，如果浮点加法印章，并有部分溢;如果浮点加法弹，但没有在IEEE样式参考，并有部分溢;如果浮点加法5参考轮在IEEE的风格，并有部分溢。参考通常5。
参数：double.guard
the number of guard digits for multiplication with truncating arithmetic. It is 1 if floating-point arithmetic truncates and more than double digits base-double.base digits participate in the post-normalization shift of the floating-point significand in multiplication, and 0 otherwise.
后卫数字乘法运算截断。这是1如果浮点运算的截断和多double digits基double.base位数乘法，浮点尾数正常化后的转变，否则为0参加。
参数：double.ulp.digits
the largest negative integer i such that 1 + double.base ^ i != 1, except that it is bounded below by -(double.digits + 3). Normally -52.
最大的负整数i等1 + double.base ^ i != 1，除了它是界-(double.digits + 3)下面。通常-52。
参数：double.neg.ulp.digits
the largest negative integer i such that 1 - double.base ^ i != 1, except that it is bounded below by -(double.digits + 3). Normally -53.
最大的负整数i等1 - double.base ^ i != 1，除了它是界-(double.digits + 3)下面。通常-53。
参数：double.exponent
the number of bits (decimal places if double.base is 10) reserved for the representation of the exponent (including the bias or sign) of a floating-point number. Normally 11.
一个浮点数指数（包括偏见或符号）表示保留的位数（小数double.base如果是10）。通常11。
参数：double.min.exp
the largest in magnitude negative integer i such that double.base ^ i is positive and normalized. Normally -1022.
幅度负整数的最大i等double.base ^ i是积极和规范化。通常-1022。
参数：double.max.exp
the smallest positive power of double.base that overflows. Normally 1024.
double.base，溢出的最小的积极力量。通常1024。
参数：integer.max
the largest integer which can be represented. Always 2147483647.
可以表示的最大整数。总是2147483647。
参数：sizeof.long
the number of bytes in a C long type: 4 or 8 (most 64-bit systems, but not Windows).
：long或4（64位系统在C8类型的字节数，而不是Windows）。
参数：sizeof.longlong
the number of bytes in a C long long type. Will be zero if there is no such type, otherwise usually 8.
在一个Clong long类型的字节数。如果有没有这样的类型，否则通常8将是零。
参数：sizeof.longdouble
the number of bytes in a C long double type. Will be zero if there is no such type, otherwise possibly 12 (most 32-bit builds) or 16 (most 64-bit builds).
在一个Clong double类型的字节数。如果有没有这样的类型，否则可能12（最32位版本）或16（64位版本），将是零。
参数：sizeof.pointer
the number of bytes in a C SEXP type. Will be 4 on 32-bit builds and 8 on 64-bit builds of R.
在一个CSEXP类型的字节数。将是432位版本和864位R的建立
注意----------Note----------
sizeof.longdouble only tells you the amount of storage allocated for a long double (which are used internally by R for accumulators in e.g. sum, and can be read by readBin). Often what is stored is the 80-bit extended double type of IEC 60559, padded to the double alignment used on the platform — this seems to be the case for the common R platforms using ix86 and x86_64 chips.
sizeof.longdouble只告诉你长的双重分配（内部使用蓄能由R的存储量，例如sum，可以读readBin）。往往是存储的是80位扩展的IEC 60559填充到平台上使用双对齐，双类型 - 这似乎是常见的R使用ix86和x86_64芯片平台的情况下。
参考文献----------References----------
MACHAR: A subroutine to dynamically determine machine parameters. Transactions on Mathematical Software, 14, 4, 303–311.
参见----------See Also----------
.Platform for details of the platform.
.Platform平台的细节。
举例----------Examples----------
.Machine
## or for a neat printout[＃或一个整洁的打印]
noquote(unlist(format(.Machine)))
转载请注明:出自 生物统计家园网(http://www.biostatistic.net)。
注：
注1：为了方便大家学习，本文档为生物统计家园网机器人LoveR翻译而成，仅供个人R语言学习参考使用，生物统计家园保留版权。
注2：由于是机器人自动翻译，难免有不准确之处，使用时仔细对照中、英文内容进行反复理解，可以帮助R语言的学习。
注3：如遇到不准确之处，请在本贴的后面进行回帖，我们会逐渐进行修订。
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发表于 2012-2-16 20:55:11
