通过从R中给定列中提取字符来循环创建列/变量 [英] Loop to create columns/variables by extracting characters from given column in R

问题描述

我的数据集如下所示：

 关键日期人口普查j 
 1：01_35004_10-14 _ + _ M 11NOV2001 2.934397 01 
 2：01_35004_10-14 _ + _ M 06JAN2002 3.028231 01 
 3：01_35004_10-14 _ + _ M 07APR2002 3.180712 01 
 4：01_35004_10-14 _ + _ M 02JUN2002 3.274546 01 
 5： 01_35004_10-14 _ + _ M 28JUL2002 3.368380 01 
 6：01_35004_10-14 _ + _ M 22SEP2002 3.462214 01 
 7：01_35004_10-14 _ + _ M 22DEC2002 3.614694 01 
 8：01_35004_10-14 _ + _ M 16FEB2003 3.708528 01 
 9：01_35004_10-14 _ + _ M 13JUL2003 3.954843 01 
 10：01_35004_10-14 _ + _ M 07SEP2003 4.048677 01 
  

列key中的某些字符对应于不同的变量。
例如：01是州，
35004是邮政编码，
10-14是年龄组，
+是比赛，
M是性别

我想提取每个字符为它们创建单独的变量（例如，填充01的状态列，填充35004的Zip Code列等）

这是我的代码：

pre code var = c（ （$ Var）{
play $ j = gsub（_。* $，，打$ key

code
$ b显然这是不正确的。我希望循环遍历key列中的每个观测值，并生成一个变量，其中包含与变量相关联的提取字符。

解决方案 read.csv ：

 ＃您的数据摘录（仅包含模型点坐标的坐标列）
x < -  c（01_35004_10-14 _ + _ M，01_35004_10-14 _ + _ M）
 
＃简单的方法是将字符串视为CSV行:-) $ b $由<  -  read.csv（text = x，sep =_，header = FALSE）
 
＃修正错误的列名
名（y）< -c（State，Zip_Code，Age_Group，Race，Gender）
 
 ＃现在通过使用翻译（lookup）表
 gender.lookup<  -  data.frame（gender.code = c（M，F），gender.name = c 男，女））
 
＃将重新编码的值添加为新列。注意：查找失败将被忽略
y $ GenderName<  -  gender.lookup $ gender.name [match（y $ Gender，gender.lookup $ gender.code）] 
  

因为我没有更多的查询数据在你的问题中，所以我将循环的实现留给了你的想象...（例如，使用 lapply 以及与列索引具有相同索引位置的查找表的列表）。

My data set looks like this:

                  key      date   census  j
1: 01_35004_10-14_+_M 11NOV2001 2.934397 01
2: 01_35004_10-14_+_M 06JAN2002 3.028231 01
3: 01_35004_10-14_+_M 07APR2002 3.180712 01
4: 01_35004_10-14_+_M 02JUN2002 3.274546 01
5: 01_35004_10-14_+_M 28JUL2002 3.368380 01
6: 01_35004_10-14_+_M 22SEP2002 3.462214 01
7: 01_35004_10-14_+_M 22DEC2002 3.614694 01
8: 01_35004_10-14_+_M 16FEB2003 3.708528 01
9: 01_35004_10-14_+_M 13JUL2003 3.954843 01
10: 01_35004_10-14_+_M 07SEP2003 4.048677 01

Certain characters within the column "key" correspond to different variables. For instance: 01 is the State, 35004 is the Zip Code, 10-14 is the Age Group, + is the Race, M is the Gender

I want to extract each of these characters to create separate variables for them (i.e. a column for state filled with 01, a column for Zip Code filled with 35004, etc)

Here is my code:

Var = c("State","Zip_Code", "Age_Group", "Race", "Gender")
for(j in Var){
play$j = gsub("_.*$","",play$key) 
}

Clearly this is not correct. I would like the loop to iterate through each observation in the "key" column and produce a variable with the extracted character associated with the variable.

解决方案

The basic solution (without expecting a good performance) uses read.csv:

# excerpt of your data (only the "coordinate" column containing the model point coordinates)
x <- c("01_35004_10-14_+_M", "01_35004_10-14_+_M")

# simple way is treating the string as CSV row :-)
y <- read.csv(text = x, sep="_", header=FALSE)

# Fix the wrong column names
names(y) <- c("State","Zip_Code", "Age_Group", "Race", "Gender")

# Now recode one example column by using translation ("lookup") table
gender.lookup <- data.frame( gender.code=c("M", "F"), gender.name=c("Male", "Female"))

# Add the recoded value as new column. Note: Lookup failures are ignored
y$GenderName <- gender.lookup$gender.name[match(y$Gender, gender.lookup$gender.code)]

I am leaving the implementation of the loop to your imagination since I don't have more lookup data in your question... (e. g. use lapply and a list of lookup tables with the same index positions as the column indices).

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