I have a data frame like this:
df = data.frame(a=1:3, b=2:4, c=3:5)
I am selecting columns from that data frame using something akin to:
df[, c(T, F, T)]
This works fine as long as there are at least two columns to be returned; but, if I do this for example:
df[, c(T, F, F)]
...我突然间只得到了一个矢量 而不是一个数据.框架。
通常这样很好(甚至更理想), 但是因为我需要结果成为数据. 框架,
是否有办法可以阻止 R 自动转换为向量, 用于单列选择?
这很简单。 附加 < code>, 投放 = FALSE 到您的子设置 。
例如:
df[, c(T, F, F, F, f, f, drop = FALSE]
也为矩阵工作。
另外,如果没有逗号,即 df[c(T,F,F)],则返回一个数据框架,但听起来你有些新数据框架可以有一个或几个列的情况。所以请使用上方的下划选项。
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