（我是R的新手。）
我不知道为什么会出现以下错误：
> apps.rsd.c <- sqldf("SELECT appid FROM apps.rsd WHERE rcount > 50")
Error in sqliteExecStatement(con, statement, bind.data) :
RS-DBI driver: (error in statement: no such table: apps.rsd)
我认为这些方法可能会有所帮助，我尝试将它们与允许我使用sqldf的数据框进行比较，但没有发现导致错误的原因：
> dput(head(apps.rsd))
structure(list(appid = c(173L, 717L, 996L, 209L, 602L, 255L),
cid = c(4L, 15L, 21L, 5L, 13L, 6L), price = c(0, 0, 0, 1.99,
0, 0.76), count = c(411, 411, 210, 18, 921, 22), sum = c(1226,
1870, 871, 66, 3948, 86), mean = c(2.98296836982968, 4.54987834549878,
4.14761904761905, 3.66666666666667, 4.28664495114007, 3.90909090909091
), sd = c(1.73897694746568, 0.958668345866094, 1.31370760232218,
1.7950549357115, 1.33373734360862, 1.62114131819336), rcount = c(3,
3, 3, 5, 5, 7), rsum = c(7, 0, 0, 13, 0, 19), rsd = c(2.3094010767585,
2.3094010767585, 2.3094010767585, 2.19089023002066, 2.19089023002066,
2.1380899352994)), .Names = c("appid", "cid", "price", "count",
"sum", "mean", "sd", "rcount", "rsum", "rsd"), class = c("data.table",
"data.frame"), row.names = c(NA, -6L), .internal.selfref = <pointer: 0x7fd3bc807b78>)
> str(apps.rsd)
Classes ‘data.table’ and 'data.frame': 1518 obs. of 10 variables:
$ appid : int 173 717 996 209 602 255 1473 442 672 772 ...
$ cid : int 4 15 21 5 13 6 31 10 14 17 ...
$ price : num 0 0 0 1.99 0 0.76 0 7.98 0 0.75 ...
$ count : num 411 411 210 18 921 22 113 54 564 33 ...
$ sum : num 1226 1870 871 66 3948 ...
$ mean : num 2.98 4.55 4.15 3.67 4.29 ...
$ sd : num 1.739 0.959 1.314 1.795 1.334 ...
$ rcount: num 3 3 3 5 5 7 7 2 2 2 ...
$ rsum : num 7 0 0 13 0 19 0 5 0 0 ...
$ rsd : num 2.31 2.31 2.31 2.19 2.19 ...
- attr(*, ".internal.selfref")=<externalptr>
在SQL中，点是运算符，而不是名称中的合法字符，因此请apps.rsd用单引号引起来（或将其重命名为其中没有点的名称）：
sqldf("SELECT appid FROM 'apps.rsd' WHERE rcount > 50")
这是一个可重现的示例。请注意，我删除了数据帧末尾的奇怪的外部指针。（那是怎么到达那里的？）
apps.rsd <-
structure(list(appid = c(173L, 717L, 996L, 209L, 602L, 255L),
cid = c(4L, 15L, 21L, 5L, 13L, 6L), price = c(0, 0, 0, 1.99,
0, 0.76), count = c(411, 411, 210, 18, 921, 22), sum = c(1226,
1870, 871, 66, 3948, 86), mean = c(2.98296836982968, 4.54987834549878,
4.14761904761905, 3.66666666666667, 4.28664495114007, 3.90909090909091
), sd = c(1.73897694746568, 0.958668345866094, 1.31370760232218,
1.7950549357115, 1.33373734360862, 1.62114131819336), rcount = c(3,
3, 3, 5, 5, 7), rsum = c(7, 0, 0, 13, 0, 19), rsd = c(2.3094010767585,
2.3094010767585, 2.3094010767585, 2.19089023002066, 2.19089023002066,
2.1380899352994)), .Names = c("appid", "cid", "price", "count",
"sum", "mean", "sd", "rcount", "rsum", "rsd"), class = c("data.table",
"data.frame"), row.names = c(NA, -6L))
library(sqldf)
sqldf("SELECT appid FROM 'apps.rsd' WHERE rcount > 50")
输出为：
[1] appid
<0 rows> (or 0-length row.names)
或重命名：
apps_rsd <- apps.rsd
sqldf("SELECT appid FROM apps_rsd WHERE rcount > 50")
给出相同的输出。
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我来说两句