R data.table'：='在直接调用中工作，但在包中的相同功能失败 [英] R data.table ':=' works in direct call, but same function in a package fails

问题描述

使用R的data.table包，

Using R's data.table package,

这适用于：

instruction = "a = data.table(name=1:3, value=1:3, blah=1:3); a[,c('value', 'blah'):=NULL]"
eval(parse(text=instruction))
#   name
#1:    1
#2:    2
#3:    3

这适用于：

myFunc = function(instruction) {
eval(parse(text=instruction))
}
myFunc(instruction)
#   name
#1:    1
#2:    2
#3:    3

现在，将此函数放入一个包， ，并尝试调用它。这不工作：

Now, put this function into a package, load it, and try to call it. This doesn't work:

myFuncInPackage(instruction)
#Error in `:=`(c("value", "blah"), NULL) : 
#  Check that is.data.table(DT) == TRUE. Otherwise, := and `:=`(...) are defined for use in j, once only and in particular ways. See help(":=").

为什么？

编辑：@Roland指出，在包中添加data.table 依赖字段使其工作。但是，我不认为这是一个伟大的解决方案，因为包实际上不依赖，需要或使用data.table。我只是想要能够使用data.table与包。

@Roland points out that adding data.table in the package Depends field makes it work. However, I don't think this is a great solution because the package doesn't really depend on, require, or use data.table. I just want to be able to use data.table with the package.

此外，其他一切与data.table工作正常的函数，只是不是：= 运算符。

In addition, everything else with data.table works fine in the function, just not the := operator.

所以我想一个后续问题可能是：我应该添加data.table包我写，使data.tables工作作为预期在该包的功能？

So I guess a followup question could be: should I add data.table to the Depends of every package I write, so that data.tables work as expected within functions of that package? This doesn't seem right... what is the correct way to approach this?

推荐答案

我有同样的问题，我解决了它将 data.table 添加到导入和取决于。我的 data.table 版本是 1.9.6

I had same problem and I solved it adding data.table to Imports and Depends:. My data.table version is 1.9.6

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