sqldf()失败，并显示“找不到函数”sqldf错误

Question

下面是我想要运行的代码。这是Coursera的代码。我无法在以下代码中运行sqldf函数：-

data = read.delim(file = 'purchases.txt', header = FALSE, sep = '\t', dec = '.')
str(data)

colnames(data) = c('customer_id', 'purchase_amount', 'date_of_purchase')
data$date_of_purchase = as.Date(data$date_of_purchase, "%Y-%m-%d")
data$days_since       = as.numeric(difftime(time1 = "2016-01-01",
                                        time2 = data$date_of_purchase,
                                        units = "days"))

head(data)
summary(data)

library(sqldf)

customers = sqldf("SELECT customer_id ,
                      MIN(days_since) AS 'recency',
                      COUNT(*) AS 'frequency',
                      AVG(purchase_amount) AS 'amount'
               FROM data GROUP BY 1")

Answer 1

用户必须在R中安装sqldf包，才能在使用library()函数加载sqldf()函数后使用它。

要在R中安装sqldf，请使用install.packages()函数。

下面是操作码的一个完全可重现的版本，包括用于安装sqldf的install.packages()

textFile <- "
001,42.5,2017-01-01
001,38.7,2017-05-02
002,47.9,2017-06-05"

# commented out original data read section
# data = read.delim(file = 'purchases.txt', header = FALSE, sep = '\t', dec = '.')
# str(data)

# replace with inline data and read.csv()
data <- read.csv(text=textFile,header=FALSE,stringsAsFactors=FALSE)

colnames(data) = c('customer_id', 'purchase_amount', 'date_of_purchase')
data$date_of_purchase = as.Date(data$date_of_purchase, "%Y-%m-%d")
data$days_since       = as.numeric(difftime(time1 = "2016-01-01",
                                            time2 = data$date_of_purchase,
                                            units = "days"))

head(data)
summary(data)

# only need to run install.packages() once
install.packages("sqldf")
library(sqldf)

customers = sqldf("SELECT customer_id ,
                      MIN(days_since) AS 'recency',
                      COUNT(*) AS 'frequency',
                      AVG(purchase_amount) AS 'amount'
               FROM data GROUP BY 1")
customers

对输出执行...and操作：

> customers
  customer_id   recency frequency amount
1           1 -486.7917         2   40.6
2           2 -520.7917         1   47.9
>