如何通过R中字符串的最后一个字符对数据帧进行子集化

Question

R-user,

I have this dataframe:

head(Niger_Meteo_98.11)
  X.ID_punto    MM.GG.AA T2m_max  
1          1    01/01/98 303.235 
2          2    01/01/99 303.356 
3          3    01/01/00 303.477 
4          4    01/01/01 303.604 
5          5    01/01/02 303.759 
6          6    01/01/03 303.915 

and I need to get only values from year 2002. So, I should select, on column MM.GG.AA , those rows that end with " /02 ". I didn't find anything online...any hints? Thanks!

Answer 1

Use standard subsetting with grep , like this:

x <- read.table(text="  X.ID_punto    MM.GG.AA T2m_max  
1          1    01/01/98 303.235 
2          2    01/01/99 303.356 
3          3    01/01/00 303.477 
4          4    01/01/01 303.604 
5          5    01/01/02 303.759 
6          6    01/01/03 303.915", header=TRUE)

x[grep("/02$", x$MM.GG.AA), ]

  X.ID_punto MM.GG.AA T2m_max
5          5 01/01/02 303.759

The grep regular expression /02$ searches for string that end in /02 , since the $ indicates the end of the string.