相关疑难解决方法(0)

我经常遇到这样的结构数据:

employees <- list(
    list(id = 1,
             dept = "IT",
             age = 29,
             sportsteam = "softball"),
    list(id = 2,
             dept = "IT",
             age = 30,
             sportsteam = NULL),
    list(id = 3,
             dept = "IT",
             age = 29,
             sportsteam = "hockey"),
    list(id = 4,
             dept = NULL,
             age = 29,
             sportsteam = "softball"))

在许多情况下,此类列表可能长达数千万个项目,因此内存问题和效率始终是一个问题.

我想将列表转换为数据帧,但如果我运行:

library(data.table)
employee.df <- rbindlist(employees)

由于NULL值,我得到错误.我的正常策略是使用如下函数:

nullToNA <- function(x) {
    x[sapply(x, is.null)] <- NA
    return(x)
}

然后:

employees <- lapply(employees, nullToNA)
employee.df <- rbindlist(employees)

返回

   id dept …

我正在尝试编写一个将Null值变为NA的函数.我的一个专栏的摘要如下所示:

      a   b 
 12 210 468 

我想将12个空值更改为NA.我还有一些其他因素列,我想将Null值更改为NA,所以我从这里和那里借了一些东西来提出这个:

# change nulls to NAs
nullToNA <- function(df){

  # split df into numeric & non-numeric functions
  a<-df[,sapply(df, is.numeric), drop = FALSE]
  b<-df[,sapply(df, Negate(is.numeric)), drop = FALSE]

  # Change empty strings to NA
  b<-b[lapply(b,function(x) levels(x) <- c(levels(x), NA) ),] # add NA level
  b<-b[lapply(b,function(x) x[x=="",]<- NA),]                 # change Null to NA

  # Put the columns back together
  d<-cbind(a,b)
  d[, names(df)]
}

但是,我收到此错误:

> foo<-nullToNA(bar)  
Error in x[x == "", ] <- NA : incorrect …

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