使用 rpy2 运行 R 函数时出错

Question

我正在尝试使用 rpy2 来运行 questionr 包中的 multi.split 函数。

这是我的代码

from rpy2 import robjects
from rpy2.robjects.packages import importr

questionr = importr(str('questionr'))

data = ["red/blue", "green", "red/green", "blue/red", "red/blue", "green", "red/green", "blue/red", "red/blue", "green", "red/green", "blue/red", "red/blue", "green", "red/green", "blue/red", "red/blue", "green"]
data_vector = robjects.StrVector(data)
multi_split = questionr.multi_split
data_table = multi_split(data_vector, split_char='/')

在最后一行之后，我收到以下错误：

RRuntimeError: Error in `colnames<-`(`*tmp*`, value = c("c(\"red/blue\",_\"green\",_\"red/green\",_\"blue/red\",_\"red/blue\",_\"green\",_.blue",  : 
 'names' attribute [4] must be the same length as the vector [3]

我认为这与我发送的向量的大小有关，因为如果我删除最后一项

data = ["red/blue", "green", "red/green", "blue/red", "red/blue", "green", "red/green", "blue/red", "red/blue", "green", "red/green", "blue/red", "red/blue", "green", "red/green", "blue/red", "red/blue"]

然后运行

data_vector = robjects.StrVector(data)
multi_split = questionr.multi_split
data_table = multi_split(data_vector, split_char='/')

我没有收到任何错误消息。如果我更改“split_char”变量，例如：

data_table = multi_split(data_vector, split_char='.')

无论我发送的数组大小如何，我都不会收到错误消息。

我尝试直接在 R（使用 R-Studio）中运行匹配的代码，它运行时没有问题。 关于如何解决此问题的任何想法？

Answer 1

这似乎是因为函数multi_split（R 包中的multi.split）试图使用与第一个参数（此处为"data_vector"）关联的表达式的字符串表示。

R函数的签名是：

multi.split(var, split.char = "/", mnames = NULL)

mnames 的文档是：

给生成的变量命名。如果为 NULL，则名称为 根据原始变量名和答案计算得出。

在调用multi_split(data_vector, split_char='/') 中，嵌入式R 看不到变量名，因为这是一个Python 调用，data_vector 是一个匿名变量（只有内容，没有变量名）。

我虽然您可以指定mnames，但您检查过并且这不起作用（请参阅下面的 cmets）。这就是代码的意思：vname <- deparse(substitute(var)) 行被评估，无论是否指定 mnames：https://github.com/juba/questionr/blob/9cf09f3ffcd6c8df24182380f12d52b061c221ef/R/table.multi.R#L161

另一种方法是计算 R 表达式的使用。较早的帖子应为此提供必要的信息：What object to pass to R from rpy2?

第三种可能性是创造性地混合 Python-strings-as-R-code：

data = ["red/blue", "green", "red/green", "blue/red", "red/blue", "green", "red/green", "blue/red", "red/blue", "green", "red/green", "blue/red", "red/blue", "green", "red/green", "blue/red", "red/blue", "green"]
data_vector = robjects.StrVector(data)
# binding the R vector to a symbol in R's "GlobalEnv"
robjects.globalenv['mydata'] = data_vector
# the call is now in a Python string that is evaluated as R code
data_table = robjects.r("multi.split(data_vector, split_char='/')")