R中的值替換

Question

我是R新手，想弄清楚如何更改數據框的現有值。我在下面包含了一個快速大綱，並感謝您的幫助！

這是我目前有：

company  top_ten_advertiser 
'Company A'   'Is Top 10' 
'Company B'   'Is Top 10' 
'Company C'   'Is Top 10' 
'Company D'   'Is Top 10' 
…    … 
'Company X'  'Not Top 10' 
'Company Y'  'Not Top 10' 
'Company Z'  'Not Top 10' 

我想更改爲以下：

company  top_ten_advertiser 
'Company A'  'Top 10 Company' 
'Company B'  'Top 10 Company' 
'Company C'  'Top 10 Company' 
'Company D'  'Top 10 Company' 
…    … 
'Company X' 'Not Top 10 Company' 
'Company Y' 'Not Top 10 Company' 
'Company Z' 'Not Top 10 Company' 

Answer 1

df$top_ten_advertiser <- gsub("Is Top 10", "Top 10 Company", df$top_ten_advertiser) 

Answer 2

比方說，你的數據幀被稱爲DF。這樣做對一個字符變量：

# Add the word "Company" to all values of top_ten_advertiser 
df$top_ten_advertiser = paste(df$top_ten_advertiser, "Company", sep=" ") 
# Remove the "Is " from "Is Top 10" 
df$top_ten_advertiser = gsub("Is ", "", df$top_ten_advertiser) 

或者這一個因素變量：

# Install the plyr package if you haven't already done so using 
# install.packages("plyr") 
library(plyr) 
revalue(df$top_ten_advertiser, 
     c("Is Top 10"="Top 10 Company", "Not Top 10"="Not Top 10 Company")) 

如果你覺得痛苦的改變因素的水平，你可以在因子變量首先轉換爲字符，改變的值，然後轉換回一個因素，像這樣：

df$top_ten_advertiser = as.character(df$top_ten_advertiser) 
df$top_ten_advertiser = paste(df$top_ten_advertiser, "Company", sep=" ") 
df$top_ten_advertiser = gsub("Is ", "", df$top_ten_advertiser) 
df$top_ten_advertiser = factor(df$top_ten_advertiser) 

而且，只是爲了保證完整性，因爲馬修·倫德伯格提到用正則表達式這樣做：

tst$top_ten_advertiser = gsub("(Is)?(.*)", "\\2 Company", tst$top_ten_advertiser) 

它很簡約，但如果你是新手正則表達式，就會變得神祕。這將對字符或因子變量起作用。但是，對因子變量進行此操作會將其轉換爲字符。