为什么有时候我可以使用双变量来筛选因子变量,而在其他情况下却不能?
以下是示例数据:
dt <- data.table(id=1:9,
var=factor(81:89))
# > dt
# id var
# 1: 1 81
# 2: 2 82
# 3: 3 83
# 4: 4 84
# 5: 5 85
# 6: 6 86
# 7: 7 87
# 8: 8 88
# 9: 9 89
为什么这个有效...
dt[id %in% 1:7 & var %in% c(82, 84)]
# id var
# 1: 2 82
# 2: 4 84
...但这会导致错误吗?
dt[var %in% c(82, 84)]
# Error in bmerge(i, x, leftcols, rightcols, io <- FALSE, xo, roll = 0, :
# x.'var' is a factor column being joined to i.'V1' which is type 'double'.
# Factor columns must join to factor or character columns.`
似乎有点不一致,可能是个bug?
sessionInfo()
的输出。看起来这个问题已经在data.table_1.9.7中得到了解决。 - zx8754