问题描述
我想要伪代码，即为列Species创建标志变量。
I want to dummy code i.e. create flag variables for column Species.
我写了下面的代码：
create_dummies<-function(data, categorical_preds){
if (categorical_preds=="setosa"){data$setosa_flg<-1}
else {data$setosa_flg<-0}
if (categorical_preds=="versicolor"){data$versicolor_flg<-1}
else {data$versicolor_flg<-0}
if (categorical_preds=="virginica"){data$virginica_flg<-1}
else {data$virginica_flg<-0}
return(data)
}
create_dummies(iris,iris$Species)
我收到了警告：
Warning messages:
1: In if (categorical_preds == "setosa") { :
the condition has length > 1 and only the first element will be used
2: In if (categorical_preds == "versicolor") { :
the condition has length > 1 and only the first element will be used
3: In if (categorical_preds == "virginica") { :
the condition has length > 1 and only the first element will be used
然后我将代码更改为：
create_dummies<-function(data, categorical_preds){
ifelse(categorical_preds=="setosa",data$setosa_flg<-1,data$setosa_flg<-0)
ifelse(categorical_preds=="versicolor",data$versicolor_flg<-1,data$versicolor_flg<-0)
ifelse(categorical_preds=="virginica",data$virginica_flg<-1,data$virginica_flg<-0)
return(data)
}
create_dummies(iris,iris$Species)
这次没有警告但是新的虚拟变量总是为0。
No warning this time but the new dummy variables are always 0.
下一步我想避免硬编码所以我写了
As a next step I want to avoid hardcoding so i wrote
create_dummies<-function(data, categorical_preds){
catvar<-(unique(categorical_preds))
for (i in 1:length(catvar)){
iris[catvar[i]]<-ifelse(iris$Species==catvar[i],1,0)
}
return(data)
}
create_dummies(iris,iris$Species)
这有什么问题？
问题：
-
为什么2个版本的代码无效？
Why the 2 versions of the code is not working?
if（）{} 和 ifelse（）功能有什么区别在R？
What is difference between if(){} and ifelse() function in R?
在 ifelse（）中，如果条件为为真，如何进行多项操作？
示例： ifelse（categorical_preds ==setosa，数据$ setosa_flg< -1 print（iris $ Species ），data $ setosa_flg< -0）。
In ifelse(), if the condition is true, how can I do multiple action?
example: ifelse(categorical_preds=="setosa",data$setosa_flg<-1 print(iris$Species),data$setosa_flg<-0).
推荐答案
警告信息：
the condition has length > 1 and only the first element will be used
告诉你在如果条件相当于使用其第一个元素：
tells you that using a vector in if condition is equivalent to use its first element :
[if (v == 1)] ~ [if (v[1] == 1)] ## v here is a vector
您应该使用向量化的 ifelse 。例如，您可以这样写下您的条件：
You should use the vectorized ifelse. For example you can write your condition like this:
create_dummies<-function(data, categorical_preds){
## here I show only the first condition
data$setosa_flg <-
ifelse (categorical_preds=="setosa",1,0)
data
}
这篇关于R中if（）和ifelse（）函数之间的区别的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！