r_code

read_* 函数的参数

参考 Schouwenaars (2016)

skip and n_max

dir("datasets/")

## [1] "hotdogs.txt"        "potatoes.csv"       "potatoes.txt"      
## [4] "swimming_pools.csv" "urbanpop.xls"       "urbanpop.xlsx"

properties <- c("area", "temp", "size", "storage", "method",
                "texture", "flavor", "moistness")
library(readr)
potatoes_fragment <- read_tsv("datasets/potatoes.txt",skip = 2, n_max = 3, col_names = properties)

## Parsed with column specification:
## cols(
##   area = col_double(),
##   temp = col_double(),
##   size = col_double(),
##   storage = col_double(),
##   method = col_double(),
##   texture = col_double(),
##   flavor = col_double(),
##   moistness = col_double()
## )

potatoes_fragment

## # A tibble: 3 x 8
##    area  temp  size storage method texture flavor moistness
##   <dbl> <dbl> <dbl>   <dbl>  <dbl>   <dbl>  <dbl>     <dbl>
## 1     1     1     1       1      3     2.5    2.8       2.8
## 2     1     1     1       1      4     2.1    2.9       2.4
## 3     1     1     1       1      5     1.9    2.8       2.2

其他的 read_* 也可以加上 n_max，触类旁通。

col_types

You can manually set the types with a string, where each character denotes the class of the column: character, double, integer and logical.

这是 R 的四种数据。

# readr is already loaded

# Column names
properties <- c("area", "temp", "size", "storage", "method",
                "texture", "flavor", "moistness")

# Import all data, but force all columns to be character: potatoes_char
potatoes_char <- read_tsv("datasets/potatoes.txt", col_types = "cccccccc", col_names = properties,
                          n_max = 3
                          )

# Print out structure of potatoes_char
str(potatoes_char)

## Classes 'spec_tbl_df', 'tbl_df', 'tbl' and 'data.frame': 3 obs. of  8 variables:
##  $ area     : chr  "1" "1" "1"
##  $ temp     : chr  "1" "1" "1"
##  $ size     : chr  "1" "1" "1"
##  $ storage  : chr  "1" "1" "1"
##  $ method   : chr  "1" "2" "3"
##  $ texture  : chr  "2.9" "2.3" "2.5"
##  $ flavor   : chr  "3.2" "2.5" "2.8"
##  $ moistness: chr  "3.0" "2.6" "2.8"
##  - attr(*, "spec")=
##   .. cols(
##   ..   area = col_character(),
##   ..   temp = col_character(),
##   ..   size = col_character(),
##   ..   storage = col_character(),
##   ..   method = col_character(),
##   ..   texture = col_character(),
##   ..   flavor = col_character(),
##   ..   moistness = col_character()
##   .. )

Schouwenaars, Filip. 2016. “Importing Data in R (Part 1).” 2016. <https://www.datacamp.com/courses/importing-data-in-r-part-1>.