sample(base)
sample()所属R语言包：base
Random Samples and Permutations
随机抽样和排列
译者：生物统计家园网 机器人LoveR
描述----------Description----------
sample takes a sample of the specified size from the elements of x using either with or without replacement.
sample需要从指定的元素大小的样品x使用或无需更换。
用法----------Usage----------
sample(x, size, replace = FALSE, prob = NULL)
sample.int(n, size = n, replace = FALSE, prob = NULL)
参数----------Arguments----------
参数：x
Either a vector of one or more elements from which to choose, or a positive integer. See "Details."
无论是从中选择一个或多个元素的向量，或正整数。请参阅“详细信息”。“
参数：n
a positive number, the number of items to choose from. See "Details."
一个正数，项目数选择。请参阅“详细信息”。“
参数：size
a non-negative integer giving the number of items to choose.
给人的项目选择一个非负整数。
参数：replace
Should sampling be with replacement?
抽样应该是更换吗？
参数：prob
A vector of probability weights for obtaining the elements of the vector being sampled.
获得被采样的向量元素的概率权重向量。
Details
详情----------Details----------
If x has length 1, is numeric (in the sense of is.numeric) and x >= 1, sampling via sample takes place from 1:x. Note that this convenience feature may lead to undesired behaviour when x is of varying length in calls such as sample(x). See the examples.
如果x长度为1，是数字（感is.numeric）x >= 1，通过sample从1:x地方取样。请注意，这个方便的功能，可能会导致意外的行为时x是不同长度的要求，如sample(x)。见的例子。
Otherwise x can be any R object for which length and subsetting by integers make sense: S3 or S4 methods for these operations will be dispatched as appropriate.
否则x可以是任何R对象为length的和整数的子集，是有意义的：S3或S4这些操作方法将酌情派出。
For sample the default for size is the number of items inferred from the first argument, so that sample(x) generates a random permutation of the elements of x (or 1:x).
对于sample默认size是从第一个参数推断的项目的数量，使sample(x)生成x（或元素的随机排列<X >）。
As from R 2.11.0 it is allowed to ask for size = 0 samples with n = 0 or a length-zero x, but otherwise n > 0 or positive length(x) is required.
从R 2.11.0要求size = 0n = 0或零长度x，但另有n > 0或积极length(x)是样品必需的。
Non-integer positive numerical values of n or x will be truncated to the next smallest integer, which has to be no larger than .Machine$integer.max.
非整数的积极n或x将被截断，下一个最小的整数，其中有没有比.Machine$integer.max较大的数值。
The optional prob argument can be used to give a vector of weights for obtaining the elements of the vector being sampled. They need not sum to one, but they should be non-negative and not all zero. If replace is true, Walker's alias method (Ripley, 1987) is used when there are more than 250 reasonably probable values: this gives results incompatible with those from R < 2.2.0, and there will be a warning the first time this happens in a session.
可选prob参数可以用来给获得被采样的向量元素的权重向量。他们需要不等于一个，但他们应该非负，而不是所有零。如果replace是真实的，使用沃克的别名方法（雷普利，1987年）时，有超过250个可能的合理值，这给从R <2.2.0不相容的结果，会有一个警告第一次发生这种情况，在一个会话。
If replace is false, these probabilities are applied sequentially, that is the probability of choosing the next item is proportional to the weights amongst the remaining items. The number of nonzero weights must be at least size in this case.
replace如果是假的，这些概率应用于顺序，这是选择的下一个项目，其余项目之间的重量是成正比的概率。非零权数必须至少size在这种情况下。
sample.int is a bare interface in which both n and size must be supplied as integers.
sample.int是一个裸露的接口在这两个n和size必须提供为整数。
值----------Value----------
For sample a vector of length size with elements drawn from either x or from the integers 1:x.
sample向量的长度为size或者x或从整数1:x绘制的元素。
For sample.int, an integer vector of length size with elements from 1:n,
为sample.int，一个长度的整数向量size元素1:n，
参考文献----------References----------
The New S Language. Wadsworth & Brooks/Cole.
参见----------See Also----------
RNG about random number generation.
RNG随机数生成。
CRAN package sampling for other methods of weighted sampling without replacement.
CRAN的包sampling加权抽样等方法，无需更换。
举例----------Examples----------
x <- 1:12
# a random permutation[随机排列]
sample(x)
# bootstrap resampling -- only if length(x) > 1 ![举重采样 - 只有长度（x）> 1！]
sample(x, replace=TRUE)
# 100 Bernoulli trials[100伯努利试验]
sample(c(0,1), 100, replace = TRUE)
## More careful bootstrapping -- Consider this when using sample()[＃更谨慎的自举 - 考虑使用样本时（）]
## programmatically (i.e., in your function or simulation)![＃编程（即，在您的功能或模拟）！]
# sample()'s surprise -- example[样品（）的惊喜 - 例如]
x <- 1:10
sample(x[x > 8]) # length 2[长度为2]
sample(x[x > 9]) # oops -- length 10![糟糕 - 长度为10！]
sample(x[x > 10]) # length 0[长度为0]
## For R >= 2.11.0 only[＃R> = 2.11.0只]
resample <- function(x, ...) x[sample.int(length(x), ...)]
resample(x[x > 8]) # length 2[长度为2]
resample(x[x > 9]) # length 1[长度为1]
resample(x[x > 10]) # length 0[长度为0]
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。
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发表于 2012-2-16 19:50:02
