8  常用函数

8.1 常数

month.abb

 [1] "Jan" "Feb" "Mar" "Apr" "May" "Jun" "Jul" "Aug" "Sep" "Oct" "Nov" "Dec"

month.name

 [1] "January"   "February"  "March"     "April"     "May"       "June"     
 [7] "July"      "August"    "September" "October"   "November"  "December" 

letters

 [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r" "s"
[20] "t" "u" "v" "w" "x" "y" "z"

LETTERS

 [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S"
[20] "T" "U" "V" "W" "X" "Y" "Z"

8.2 基础

c(1,2,3,4) # 拼接

[1] 1 2 3 4

seq(0,1,by=0.25) #序列

[1] 0.00 0.25 0.50 0.75 1.00

length(1:10)

[1] 10

rep(1:2,each=5)

 [1] 1 1 1 1 1 2 2 2 2 2

rep(1:2,time=5)

 [1] 1 2 1 2 1 2 1 2 1 2

head(1:10)

[1] 1 2 3 4 5 6

tail(1:10)

[1]  5  6  7  8  9 10

is.na(c(1:10,NA))

 [1] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE  TRUE

class(mtcars)

[1] "data.frame"

dim(mtcars)

[1] 32 11

names(mtcars)

 [1] "mpg"  "cyl"  "disp" "hp"   "drat" "wt"   "qsec" "vs"   "am"   "gear"
[11] "carb"

paste(2011,1:5,01,sep='-')

[1] "2011-1-1" "2011-2-1" "2011-3-1" "2011-4-1" "2011-5-1"

str(mtcars)

'data.frame':   32 obs. of  11 variables:
 $ mpg : num  21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ...
 $ cyl : num  6 6 4 6 8 6 8 4 4 6 ...
 $ disp: num  160 160 108 258 360 ...
 $ hp  : num  110 110 93 110 175 105 245 62 95 123 ...
 $ drat: num  3.9 3.9 3.85 3.08 3.15 2.76 3.21 3.69 3.92 3.92 ...
 $ wt  : num  2.62 2.88 2.32 3.21 3.44 ...
 $ qsec: num  16.5 17 18.6 19.4 17 ...
 $ vs  : num  0 0 1 1 0 1 0 1 1 1 ...
 $ am  : num  1 1 1 0 0 0 0 0 0 0 ...
 $ gear: num  4 4 4 3 3 3 3 4 4 4 ...
 $ carb: num  4 4 1 1 2 1 4 2 2 4 ...

summary(mtcars)

      mpg             cyl             disp             hp       
 Min.   :10.40   Min.   :4.000   Min.   : 71.1   Min.   : 52.0  
 1st Qu.:15.43   1st Qu.:4.000   1st Qu.:120.8   1st Qu.: 96.5  
 Median :19.20   Median :6.000   Median :196.3   Median :123.0  
 Mean   :20.09   Mean   :6.188   Mean   :230.7   Mean   :146.7  
 3rd Qu.:22.80   3rd Qu.:8.000   3rd Qu.:326.0   3rd Qu.:180.0  
 Max.   :33.90   Max.   :8.000   Max.   :472.0   Max.   :335.0  
      drat             wt             qsec             vs        
 Min.   :2.760   Min.   :1.513   Min.   :14.50   Min.   :0.0000  
 1st Qu.:3.080   1st Qu.:2.581   1st Qu.:16.89   1st Qu.:0.0000  
 Median :3.695   Median :3.325   Median :17.71   Median :0.0000  
 Mean   :3.597   Mean   :3.217   Mean   :17.85   Mean   :0.4375  
 3rd Qu.:3.920   3rd Qu.:3.610   3rd Qu.:18.90   3rd Qu.:1.0000  
 Max.   :4.930   Max.   :5.424   Max.   :22.90   Max.   :1.0000  
       am              gear            carb      
 Min.   :0.0000   Min.   :3.000   Min.   :1.000  
 1st Qu.:0.0000   1st Qu.:3.000   1st Qu.:2.000  
 Median :0.0000   Median :4.000   Median :2.000  
 Mean   :0.4062   Mean   :3.688   Mean   :2.812  
 3rd Qu.:1.0000   3rd Qu.:4.000   3rd Qu.:4.000  
 Max.   :1.0000   Max.   :5.000   Max.   :8.000  

8.3 统计

---

#统计
x=rnorm(1000) #随机数
head(x)

[1] -1.20005554  0.39673153 -0.03092921  0.90827612  0.70780874  1.17401448

min(x)

[1] -3.528692

max(x)

[1] 3.0422

range(x)

[1] -3.528692  3.042200

mean(x)

[1] 0.01667074

median(x)

[1] 0.04793839

sd(x)

[1] 1.008562

var(x)

[1] 1.017197

quantile(x)

         0%         25%         50%         75%        100% 
-3.52869250 -0.60665337  0.04793839  0.70892757  3.04219967 

fivenum(x)

[1] -3.52869250 -0.60688274  0.04793839  0.70893170  3.04219967

table(mtcars$cyl)

 4  6  8 
11  7 14 

table(mtcars$cyl,mtcars$cyl)

   
     4  6  8
  4 11  0  0
  6  0  7  0
  8  0  0 14