sqldf中的R调用变量

Question

我需要对 sqldf 语句进行循环，为此我需要调用 sqldf 代码中的循环变量:

我的表“数据”，可能是:

data <- read.table(text ="
    loaddate DaysRange DaysRangeNext
1 2014-03-16        30            30
2 2014-03-16         0             0
3 2014-03-16         0             0
4 2014-03-16        60            NA
5 2014-04-16        30            30
6 2014-04-16         0            30
"
,header = TRUE)

然后我将 loaddate 格式化为日期:

data$loaddate<-as.Date(as.character(data$loaddate), format='%Y-%m-%d')

假设我有一个向量“loaddates”:

loaddates<- unique(sort(data$loaddate))

我需要为每个加载日期运行以下代码:

for (i in loaddates) {

sqldf("
SELECT D.LoadDate,D.DaysRange, D.DaysRangeNext, 
COUNT(*) AS clientes
FROM data AS D
WHERE D.loaddate = i
GROUP BY D.LoadDate,D.DaysRange, D.DaysRangeNext
ORDER BY D.DaysRange, D.DaysRangeNext
")        }

但我收到以下错误:

Error in sqliteSendQuery(con, statement, bind.data) : error in statement: no such column: i

有没有办法保留变量值并在循环中使用它？

谢谢。

版:

我试过:

sqldf(
strwrap(sprintf("
SELECT D.LoadDate,D.DaysRange, D.DaysRangeNext, 
COUNT(*) AS clientes 
FROM data AS D
WHERE D.LoadDate = '%s'
GROUP BY D.LoadDate,D.DaysRange, D.DaysRangeNext
ORDER BY D.DaysRange, D.DaysRangeNext
",i),simplify=TRUE,width=1000000))

但我得到了:

> [1] loaddate      DaysRange     DaysRangeNext clientes      <0 rows>
> (or 0-length row.names)

Answer 1

变量 i不会在查询中按原样替换。您需要 sprintf为其赋值。 (我也不知道您是否需要考虑断行，但只是为了确保我在下面提供它。也许您不需要 sqldf；在这种情况下，只需删除 strwrap)。

#let's assume loaddates is the following:
loaddates <- 'something'

根据需要获取查询的一种方法，即没有中断线和 i取所需的 loaddates 值:

strwrap(sprintf("
                SELECT D.LoadDate,D.DaysRange, D.DaysRangeNext, 
                COUNT(*) AS clientes
                FROM deuda AS D
                WHERE D.loaddate = '%s'
                GROUP BY D.LoadDate,D.DaysRange, D.DaysRangeNext
                ORDER BY D.DaysRange, D.DaysRangeNext
                ",i),simplify=TRUE,width=1000000)

这将输出:

[1] "SELECT D.LoadDate,D.DaysRange, D.DaysRangeNext, COUNT(*) AS clientes FROM deuda AS D WHERE D.CodEmp = 'TGG' and D.loaddate = something GROUP BY D.LoadDate,D.DaysRange, D.DaysRangeNext ORDER BY D.DaysRange, D.DaysRangeNext"

这是您在一行中需要的内容，没有中断线或变量 i未分配。

在你的循环中它应该是:

for (i in loaddates) {

strwrap(sprintf("
                SELECT D.LoadDate,D.DaysRange, D.DaysRangeNext, 
                COUNT(*) AS clientes
                FROM deuda AS D
                WHERE D.loaddate = '%s'
                GROUP BY D.LoadDate,D.DaysRange, D.DaysRangeNext
                ORDER BY D.DaysRange, D.DaysRangeNext
                ",i),simplify=TRUE,width=1000000)

}

使用您的数据集:

library(sqldf)
data <- read.table(text ="
    loaddate DaysRange DaysRangeNext
1 2014-03-16        30            30
2 2014-03-16         0             0
3 2014-03-16         0             0
4 2014-03-16        60            NA
5 2014-04-16        30            30
6 2014-04-16         0            30
"
                   ,header = TRUE,stringsAsFactors=F)

loaddates<- unique(sort(data$loaddate))

for (i in loaddates) {

  print(sqldf(
  strwrap(sprintf("
                SELECT D.LoadDate,D.DaysRange, D.DaysRangeNext, 
                COUNT(*) AS clientes
                FROM data AS D
                WHERE D.loaddate = '%s'
                GROUP BY D.LoadDate,D.DaysRange, D.DaysRangeNext
                ORDER BY D.DaysRange, D.DaysRangeNext
                ",i),simplify=TRUE,width=1000000) ))
}

输出:

    loaddate DaysRange DaysRangeNext clientes
1 2014-03-16         0             0        2
2 2014-03-16        30            30        1
3 2014-03-16        60            NA        1
    loaddate DaysRange DaysRangeNext clientes
1 2014-04-16         0            30        1
2 2014-04-16        30            30        1