Extract the first or last n characters of a string

Question

I want to extract the first  or last  n characters of a string  This would be the equivalent to Excel s LEFT   and RIGHT    A small example     create a string a  lt - paste  left    right   sep       a    1   leftright    I would like to produce b  a string which is equal to the first 4 letters of a   b    1   left    What should I do

User · Answer

You can easily obtain Right   and Left   functions starting from the Rbase package    right function  right   function  string  char        substr string nchar string - char-1  nchar string      left function  left   function  string char        substr string 1 char       you can use those two custom-functions exactly as left   and right   in excel  Hope you will find it useful

User · Answer

The stringr package provides the str sub function  which is a bit easier to use than substr  especially if you want to extract right portions of your string    R gt  str sub  leftright  1 4   1   left  R gt  str sub  leftright  -5 -1   1   right

User · Answer

If you are coming from Microsoft Excel  the following functions will be similar to LEFT    RIGHT    and MID   functions     This counts from the left and then extract n characters  str left  lt - function string  n      substr string  1  n         This counts from the right and then extract n characters  str right  lt - function string  n      substr string  nchar string  -  n - 1   nchar string         This extract characters from the middle  str mid  lt - function string  from   2  to   5        substr string  from  to        Examples  x  lt -  quot some text in a string quot  str left x  4   1   quot some quot   str right x  6   1   quot string quot   str mid x  6  9   1   quot text quot

User · Answer

See  substr  R gt  substr a  1  4   1   left

User · Answer

Make it simple and use R basic functions     To get the LEFT part   gt  substr a  1  4   1   left   gt     To get the MIDDLE part   gt  substr a  3  7   1   ftrig   gt     To get the RIGHT part   gt  substr a  5  10   1   right    The substr   function tells you where start and stop substr x  start  stop

[string] Extract the first (or last) n characters of a string

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