用rpy2运行R函数时出错

Question

我正在尝试使用rpy2运行多重分割来自questionr包的函数。你知道吗

这是我的密码

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，我得到以下错误：

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"]

然后跑

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

我没有收到错误信息。另外，如果我更改“split\u char”变量，例如：

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

无论发送的数组大小如何，我都不会收到错误消息。你知道吗

我试过直接在R中运行匹配的代码（使用R-Studio），它运行起来没有问题。 有什么办法解决这个问题吗？你知道吗

Answer 1

这似乎是因为函数multi_split（multi.split在R包中）试图使用与第一个参数相关联的表达式的字符串表示（这里是"data_vector"）。你知道吗

R函数的签名是：

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

而mnames的he文档是：

names to give to the produced variabels. If NULL, the name are computed from the original variable name and the answers.

在调用multi_split(data_vector, split_char='/')中，嵌入的R无法看到变量名，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）。你知道吗

我认为您可以指定mnames，但是您选中了，这不起作用（参见下面的注释）。代码似乎是这么说的：无论是否指定mnames，都会对行vname <- deparse(substitute(var))求值：https://github.com/juba/questionr/blob/9cf09f3ffcd6c8df24182380f12d52b061c221ef/R/table.multi.R#L161

另一种方法是计算R表达式的用法。较旧的post应该为此提供必要的位：What object to pass to R from rpy2?

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

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='/')")