R language Notes-vector manipulation

1. The basic elements of the vector are: numeric value (numeric), character (character), logical value (logical), plural type (complex)

2. Vectors do not require a defined type and can be assigned directly:

A<-c (1,2,3,4,5,-3,-4); a #数值型向量

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

B<-c ("One", "one", "one", "three"); b #字符型向量

[1] "one" "" "" Three "

C<-c (True,true,true,false); C #逻辑型向量

[1] True True True FALSE

X<-c (5,4,2); x

[1] 5 4 2

X[9]<-9;x # when Vector x is not long enough, specify a 9th element of 9

[1] 5 4 2 na na na na na 9 #自动将中间的元素补为NA

3. The vector element subscript value is starting at 1, for example: to take the x vector in the previous value is 1, then x[2]

If there is a character in a vector, the type of the vector becomes a character;

Demo_1<-c (, ' a ')

Mode (demo_1)

[1] "character"

4. Add a name to the vector:

Names (years) <-c ("Kennedy", "Johnson", "Carter", "Clinton"); years

Kennedy Johnson Carter Clinton

1960 1964 1976 1994

5. Addition and merging of vector elements

V<-c (a)

V<-c (v,55) #格式为新向量 <-(original vector, new element)

V

[1] 1 2 3 55

V1 <-C (1, 2, 3)

V2 <-C (4, 5, 6)

C (V1,V2)

[1] 1 2 3 4 5 6

>v<-c (1,2,3,3,3,4)

> Append (v,10,after=3) #在第3个向量后面加入10

[1] 1 2 3 10 3 3 4

6. If the logical variable is combined with a numeric value, it is converted to a numeric value. True turns into 1 and FALSE to 0.

Demo_2<-c (1,2,true)

Mode (demo_2) [1] "Numeric"

DEMO_2[1] 1 2 1

There is no single integer, single character concept in the R language

For example: x<-2;x<-' a '; R is all treated as a vector, except that the vector includes only a single value.

7. Generation of several special vectors

7.1 Generating Series seq ()

Seq (length=, from=, to=)

Length: Specify the number of builds

From: Refers to the point at which the build starts

To: Cutoff point

If not specified, the default condition: seq (n1,n2,by=)

N1: Start position

N2: Cut-off position

by= Specify interval

Seq (length=10,from=10,to=100)

[1] 10 20 30 40 50 60 70 80 90 100

Seq (10,100,10)

[1] 10 20 30 40 50 60 70 80 90 100

7.2 Rep (p,n) repeatedly generates P-value N times

Rep (1,10) [1] 1 1 1 1 1 1 1 1 1 1

8. Vector operations

Take the sub-vector: by subscript implementation

Take an element: X[2];(if x includes a name, note: x[2] and x[[2]];

Take a few: X[c (1,2,0)]

Take one/several elements, use-:x[-n]

9. Vector sorting

Sort (); The output is sorted after the result;

Order (); the position of each vector after the output is sorted;

A<-c (3,9,0,12,19)

Sort (a); order (a);

A<-c (3,9,0,12,19)

Order (a) [1] 3 1 2 4 5

Sort (a) [1] 0 3 9 12 19

10. Add. If two vectors are not the same during the two vectors, R automatically complements the vector with a small length until the length equals the large vector.

For example:

demo_5<-1:3;

demo_6<-2:5;

demo_7= demo_6+ demo_5;

Warning message:

In Demo_6 + demo_5:

Longer object length is not a multiple of shorter object length

demo_5<-1:3;

demo_6<-2:7;

demo_7= demo_6+ demo_5;

DEMO_7[1] 3 5 7 6 8 10

11. Extracting elements of a vector by condition

X<-c (10:1); x

[1] 10 9 8 7 6 5 4 3 2 1

X[x==3]<-25;x #将x中等于3的元素变为25

[1] 10 9 8 7 6 5 4 25 2 1

X[x=1]<-12;x #将x的第1个元素数值变为12

[1] 12 9 8 7 6 5 4 25 2 1

> letters[1:30] # Generating alphabetic sequences

[1]&NB