R技巧[01]：R生成各种常用分布随机数的方法

　　R软件一个显著的优点是它提供了丰富的随机数发生器，比SAS、Matlab方面很多，比Excel更不知方便到哪里去了。这无疑为统计学、工程学以及寿险精算学提供了很大的方便，比如我们要产生200个服从正态分布的随机数，在R里面用只需要键入“rnorm(200)”即可得到。操作如下：

>rnorm(200)

[1] -0.12071839  0.05257376 -0.23671186 -0.71413741  2.17362525 -0.25102710
[7] -1.41124223  1.78816754  0.95697026 -1.73518078 -0.71141662  1.27847876
[13] -1.50472436 -0.55267534  0.46788900  0.32977779  0.37641009 -1.22411512
[19] -1.82099431 -1.50026288......

　　rnorm()函数更通用的用法是rnorm(n,mean,sd),其中n为要产生随机数的个数，mean为所产生随机数的总体所具有的均值，sd是所产生的随机数的总体所具有的标准差。

要产生服从均值为2，标准差为3的随机数100个，在R中：

>rnorm(n=100,mean=2,sd=3)

当然也可以更简便：

>rnorm(100,2,3)

　　R软件生成各种常用分布随机数的方法

　　类似的还可以在stat包里得到更多分布的随机数，一些对应函数如下：

rexp	The Exponential Distribution
rf	The F Distribution
rgamma	The Gamma Distribution
rgeom	The Geometric Distribution
rhyper	The Hypergeometric Distribution
rlnorm	The Log Normal Distribution
rlogis	The Logistic Distribution
rmultinom	The Multinomial Distribution
rnbinom	The Negative Binomial Distribution
rnorm	The Normal Distribution
rpois	The Poisson Distribution
rsignrank	Distribution of the Wilcoxon Signed Rank Statistic
rt	The Student t Distribution
runif	The Uniform Distribution
rweibull	The Weibull Distribution
rwilcox	Distribution of the Wilcoxon Rank Sum Statistic
rexp	The Exponential Distribution
rf	The F Distribution
rgamma	The Gamma Distribution
rgeom	The Geometric Distribution
rhyper	The Hypergeometric Distribution
rlnorm	The Log Normal Distribution
rlogis	The Logistic Distribution
rmultinom	The Multinomial Distribution
rnbinom	The Negative Binomial Distribution
rnorm	The Normal Distribution
rpois	The Poisson Distribution
rsignrank	Distribution of the Wilcoxon Signed Rank Statistic
rt	The Student t Distribution
runif	The Uniform Distribution
rweibull	The Weibull Distribution
rwilcox	Distribution of the Wilcoxon Rank Sum Statistic

用法大致一样。