R Language Learning (5)-strings and Factors

String and factor 1. Create a string

> C ("hello", "world") [1] "hello" "world"

Use the paste function to connect to a string

> Paste (C ("hello", "Hi"), "world") [1] "Hello World" "Hi world"

> Paste (C ("hello", "Hi"), "world", SEP = "-") [1] "hello-World" "Hi-World"> paste (C ("hello", "Hi"), "world", collapse = "! ") [1]" Hello world! Hi world "> paste0 (C (" hello "," Hi ")," world ") # The paste0 function can remove the separator [1]" helloworld "" hiworld"

Tostring function print string

> X [1] 1 4 9 16 25> tostring (x) [1] "1, 4, 9, 16, 25"> tostring (x, width = 2) # width indicates the maximum character length [1] "1 ,...."

The toupper and tolower functions change the case sensitivity.

> Toupper ("Hello world! ") [1]" Hello world! "> Tolower (" Hello world! ") [1]" Hello world! "

Use substring and substr to intercept a string
Use strsplit to separate strings

2. formatc Function

> POW <-> (power_of_e <-exp (POW) [1] 2.718282 7.389056 20.085537> formatc (power_of_e) [1] "2.718" "7.389" "20.09"> formatc (power_of_e, digits = 3) # retain three numbers [1] "2.72" "7.39" "20.1"> formatc (power_of_e, digits = 3, width = 10) # Add a space [1] "2.72" "7.39" "20.1"> formatc (power_of_e, digits = 3, format = "e ") # scientific notation [1] "2.718e + 00" "7.389e + 00" "2.009e + 01"> formatc (power_of_e, digits = 3, flag = "+ ") + Add + [1] "+ 2.72" "+ 7.39" "+ 20.1"

Sprintf Function

> Sprintf ("% S % d % E", "Euler's constant to the power", pow, power_of_e) [1] "Euler's constant to the power 1 2.718282e + 00" [2] "Euler's constant to the power 2 7.389056e + 00" [3] "Euler's constant to the power 3 2.008554e + 01"

The format and prettynum functions are also used to format numbers.

3. factor: a factor is a special variable type used to store class variables. Sometimes it is like a string or an integer to create a factor.
Data box automatic factor Creation

> (Heights <-data. frame (height_cm = C (153,181,150,172,165), Gender = C ("female", "male", "male", "female", "male ")))

Height_cm gender

1 153 female

2 181 male

3 150 male

4 172 female

5 165 male

> Class (heights $ gender)

[1] "factor"

> Heights $ gender

[1] Female Male

Levels: Female Male # female and male are called Factor Levels.

Factor Function creation factor

> Gender_char <-C ("female", "male", "male", "female", "male ")

> (Gender_factor <-factor (gender_char ))

[1] Female Male

Levels: Female Male