[R] Select part of character row name in a data frame

[Enrico Schumann]

Quoting Francesca PANCOTTO <f.pancotto at unimore.it>:

> Dear R contributors,
>
> I have a problem in selecting in an efficient way, rows of a data  
> frame according to a condition,
> which is a part of a row name of the table.
>
> The data frame is made of 64 rows and 2 columns, but the row names  
> are very long but I need to select them according to a small part of  
> it and perform calculations on the subsets.
>
> This is the example:
> 											X			Y
> "Unique to strat          "                                           
>           0.0482        28.39
> "Unique to crt.dummy        "                                         
>           0.0441        25.92
> "Unique to gender                   "                                 
>           0.0159         9.36
> "Unique to age                       "                                
>           0.0839        49.37
> "Unique to gg_right1              "                                   
>           0.0019         1.10
> "Unique to strat:crt.dummy                 "                          
>           0.0689        40.54
> "Common to strat, and crt.dummy         "                             
>          -0.0392       -23.09
> "Common to strat, and gender         "                                
>          -0.0031        -1.84
> "Common to crt.dummy, and gender     "                                
>           0.0038         2.21
> "Common to strat, and age                 "                           
>           0.0072         4.21
>
> X and Y are the two columns of variables, while “Unique to strat”,  
> are the row names. I am interested to select for example those rows
> whose name contains “strat” only. It would be very easy if these  
> names were simple, but they are not and involve also spaces.
> I tried with select matches from dplyr but works for column names  
> but I did not find how to use it on row names, which are of course  
> character values.
>
> Thanks for any help you can provide.
>
> ----------------------------------
> Francesca Pancotto, PhD
>

Use ?grep or ?grepl:

     df[grep("strat", row.names(df)), ]

(in which 'df' is your data frame)


-- 
Enrico Schumann
Lucerne, Switzerland
http://enricoschumann.net