[R] retrieve rows from frame assuming criterion

[Marc Schwartz]

On Fri, 2004-07-23 at 08:36, Luis Rideau Cruz wrote:
> Hi all,
> 
> I have a data frame in which one column(PUNTAR) is of character type.
> What I want is to retrieve is the frame but only with those rows
> matching elements of PUNTAR with a list characters (e.g
> c("IX49","IX48") )
> 
> Year    TUR  STODNR   PUNTAR
> 1994  9412 94020061     IX49
> 1994  9412 94020062     IX48
> 1994  9412 94020063      X32
> 1994  9412 94020065      X23
> 1994  9412 94020066      X27
> 1994  9412 94020067     XI19
> 1994  9412 94020068     XI16
> 1994  9412 94020069     XI14
> 1994  9412 94020070      XI8
> 1994  9412 94020071      X25
> 1994  9412 94020072      X18
> 1994  9412 94020073     II23
> 1994  9412 94020074    XII33
> 1994  9412 94020075    XII31
> 
> "my.function"("frame") should be then equal to 
> 
> Year TURNR   STODNR M_PUNTAR
> 1994  9412 94020061     IX49
> 1994  9412 94020062     IX48
> 
> Thank you in advance


For a simple subset like this, something like the following, presuming
that your data frame is called MyData:

 MyData[MyData$PUNTAR %in% c("IX49", "IX48"), ]
  Year  TUR   STODNR PUNTAR
1 1994 9412 94020061   IX49
2 1994 9412 94020062   IX48

This basically says to select only those rows where the value of
MyData$PUNTAR is in c("IX49", "IX48").

If you need to engage in more complex boolean comparisons for
subsetting, especially on multiple columns, then the function subset()
would be better suited.

HTH,

Marc Schwartz