gsub不会替换列中的名称

Question

使用R时，具有列Certificate...HQA的my data frame capstone3具有以下级别：

levels(capstone3$Certificate...HQA)

 [1] "CUM LAUDE"                     "DIPLOM"                       
 [3] "DOCTORATE"                     "GRADUATE DIPLOMA"             
 [5] "HIGHEST HONS"                  "HONOURS (DISTINCTION)"        
 [7] "HONOURS (HIGHEST DISTINCTION)" "HONS"                         
 [9] "HONS I"                        "HONS II"                      
[11] "HONS II LOWER"                 "HONS II UPPER"                
[13] "HONS III"                      "HONS UNCLASSIFIED"            
[15] "HONS WITH MERIT"               "MAGNA CUM LAUDE"              
[17] "MASTER'S DEGREE"               "OTHER HONS"                   
[19] "PASS DEGREE"                   "PASS WITH CREDIT"             
[21] "PASS WITH DISTINCTION"         "PASS WITH HIGH MERIT"         
[23] "PASS WITH MERIT"               "SUMMA CUM LAUDE" 

我写了一个代码来减少级别的数量，用级别9替换级别7，用级别12替换级别6，依此类推：

capstone3$Certificate...HQA <- as.factor(capstone3$Certificate...HQA)

capstone3$Certificate...HQA <- gsub("HONOURS (HIGHEST DISTINCTION)","HONS I", capstone3$Certificate...HQA)

capstone3$Certificate...HQA <- gsub("HONOURS (DISTINCTION)","HONS II UPPER", capstone3$Certificate...HQA)

capstone3$Certificate...HQA <- gsub("HONS WITH MERIT","HONS II LOWER", capstone3$Certificate...HQA)

但是上面的gsub代码并没有替换列中的名字，有人能指出我代码的问题吗？

Answer 1

圆括号()是正则表达式中用于创建组的特殊字符。如果有文字圆括号，则需要使用\\对它们进行转义

gsub("HONOURS \\(HIGHEST DISTINCTION\\)","HONS I", capstone3$Certificate...HQA)

或者像@ManuelBickel一样:使用fixed = TRUE，模式是一个字符串，将按原样匹配。

gsub("HONOURS (HIGHEST DISTINCTION)","HONS I", capstone3$Certificate...HQA, fixed = TRUE)