1

例如：

require(RevoScaleR)

# Create a data frame
set.seed(100)
myData = data.frame(x = 1:100, y = rep(c("a", "b", "c", "d"), 25),
                     z = rnorm(100), w = runif(100))

# Create a multi-block .xdf file from the data frame
inputFile = file.path(tempdir(), "testInput.xdf")
rxDataStep(inData = myData, outFile = inputFile, rowsPerRead = 50, 
           overwrite = TRUE)

# Square the values in the column "z"; this works fine
rxDataStep(inData = inputFile, outFile = inputFile, overwrite = TRUE,
           transforms = list(z = z^2))

# Define a squaring function and try to use it to repeat the previous step:
myFun = function(x) x^2
rxDataStep(inData = inputFile, outFile = inputFile, overwrite = TRUE,
           transforms = list(z = myFun(z)))

最后一步因错误而崩溃

Error in transformation function: Error in eval(expr, envir, enclos) : could not find function "myFun"

的文档rxDataStep指出“与所有表达式一样，转换......可以使用expression函数在函数调用之外定义。” 但我不知道如何实施这个建议，也找不到一个例子。例如，以下内容不起作用：

myFun = expression(function(x) x^2)
rxDataStep(inData = inputFile, outFile = inputFile, overwrite = TRUE,
           transforms = list(z = myFun(z)))
4

2 回答 2

2

您当然可以将表达式传递给transform在函数调用之外创建的表达式。

它看起来像这样：

myFun <- expression(
  list(x2 = x^2,
       z2 = z^2))
rxDataStep(inData = inputFile, outFile = inputFile, overwrite = TRUE,
           transforms = myFun)

如果您想像在第一个示例中那样传递一个函数，它看起来像这样：

myFun2 <- function(dataList){
  dataList$x2 <- dataList$x^2
  dataList$z2 <- dataList$z^2
  dataList
}
rxDataStep(inData = inputFile, outFile = inputFile, overwrite = TRUE,
           transformFunc = myFun2)
于 2015-01-22T21:26:27.657 回答
1

不知道为什么会这样！

env <- new.env()
env$myFun <- function(x) x^2
rxDataStep(inData = inputFile, outFile = inputFile, overwrite = TRUE,
           transforms = list(z = myFun(z)), transformEnvir=env)
于 2014-09-24T18:33:20.243 回答