Try R

Try R

我知道我是个懒人，突然间就不想写博客了，停了差不多三个月，现在可以重新开始了：

• 课程来源:http://tryr.codeschool.com/levels/1/challenges/1

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Chapter 1

try some simple math

R is a language and environment for statistical computing and graphics,It’s an open source solution to data analysis that’s supported by a large and active worldwide research community.

Expressions 1.1

> 1 + 1
[1] 2

> "Arr, matey!"
[1] "Arr, matey!"

> 6 * 7
[1] 42

Logical Values 1.2

> 3 < 4
[1] TRUE

> 2 + 2 == 5
[1] FALSE

> T == TRUE
[1] TRUE 
# T and F are shorthand for TRUE and FALSE.

Variables 1.3

> x <- 42
# Type x <- 42 to store a value in x.

> x / 2
[1] 21

> x <- "Arr, matey!"
> x
[1] "Arr, matey!"

> x <- TRUE
# assigning the TRUE logical value to x

Functions 1.4

# sum
> sum(1, 3, 5)
[1] 9

# rep
# time
> rep("Yo ho!", times = 3)
[1] "Yo ho!" "Yo ho!" "Yo ho!"

# sqrt
> sqrt(16)
[1] 4

Help 1.5

> help(sum)
sum {base}  R Documentation
Sum of Vector Elements

Description
sum returns the sum of all the values present in its arguments.

Usage
sum(..., na.rm = FALSE)

Arguments
... 
numeric or complex or logical vectors.
na.rm   
... 

> example(min)
min> require(stats); require(graphics)
min>  min(5:1, pi) #-> one number
[1] 1
min> pmin(5:1, pi) #->  5  numbers
[1] 3.141593 3.141593 3.000000 2.000000 1.000000
min> x <- sort(rnorm(100));  cH <- 1.35
min> pmin(cH, quantile(x)) # no names
[1] -2.4918436 -0.9161651 -0.1945227  0.4487425  1.3500000
min> pmin(quantile(x), cH) # has names
        0%        25%        50%        75%       100% 
-2.4918436 -0.9161651 -0.1945227  0.4487425  1.3500000 
min> plot(x, pmin(cH, pmax(-cH, x)), type = "b", main =  "Huber's function")
Hit <Return> to see next plot:  
min> cut01 <- function(x) pmax(pmin(x, 1), 0)
min> curve(      x^2 - 1/4, -1.4, 1.5, col = 2)

Hit <Return> to see next plot: 

min> curve(cut01(x^2 - 1/4), col = "blue", add = TRUE, n = 500)

min> ## pmax(), pmin() preserve attributes of *first* argument
min> D <- diag(x = (3:1)/4) ; n0 <- numeric()

min> stopifnot(identical(D,  cut01(D) ),
min+           identical(n0, cut01(n0)),
min+           identical(n0, cut01(NULL)),
min+           identical(n0, pmax(3:1, n0, 2)),
min+           identical(n0, pmax(n0, 4)))

> help(rep)
rep {base}  R Documentation
Replicate Elements of Vectors and Lists
Description
rep replicates the values in x. It is a generic function, and the (internal) default method is described here.
rep.int and rep_len are faster simplified versions for two common cases. They are not generic.
Usage
rep(x, ...)
rep.int(x, times)
rep_len(x, length.out)

Files 1.6

> list.files()
 [1] "1.png"                "123.xlsx"             "1234.xlsx"           
 [4] "Bluetooth 交换文件夹" "desktop.ini"          "down"                
 [7] "GIS DataBase"         "IISExpress"           "JDdongdong"          
[10] "My eBooks"            "My Music"             "My Pictures"         
[13] "My Videos"            "My Web Sites"         "OneNote 笔记本"      
[16] "OriginLab"            "R"                    "ServerConfig"        
[19] "Tencent Files"        "VisIt"                "Visual Studio 2013"