R help - Oct 2009 - how to have 'match' ignore no-matches

Hi all,
I think this is a very basic question, but I'm new to this so please bear
with me.

I'm using match to translate elements of a data frame using a lookup table.
If the content of a particular cell is not found in the lookup table, the
function returns NA. I'm wondering how I can just ignore those cells, and
return the original contents if no match is found in the lookup table.

Many thanks in advance, this site has been extremely helpful for me so far,
Jill

Jill Hollenbach, PhD, MPH
    Assistant Staff Scientist
    Center for Genetics
    Children's Hospital Oakland Research Institute
    jhollenbach at chori.org
-- 
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On Oct 5, 2009, at 4:01 PM, Jill Hollenbach wrote:
>
> Hi all,
> I think this is a very basic question, but I'm new to this so please  
> bear
> with me.
>
> I'm using match to translate elements of a data frame using a lookup  
> table.
> If the content of a particular cell is not found in the lookup  
> table, the
> function returns NA. I'm wondering how I can just ignore those  
> cells, and
> return the original contents if no match is found in the lookup table.
Can you construct a simple example (with sufficient complexity and  
lack of matches)  that can be cut-and-pasted into the console along  
with specification of how you want your results?

I cannot understand what you are asking for a "translat[ion] of a  
dataframe" and when you request the "return [of] the original contents
if no match is found in the lookup table."

-- 
David Winsemius, MD
Heritage Laboratories
West Hartford, CT

On 6/10/2009, at 9:01 AM, Jill Hollenbach wrote:
>
> Hi all,
> I think this is a very basic question, but I'm new to this so  
> please bear
> with me.
>
> I'm using match to translate elements of a data frame using a  
> lookup table.
> If the content of a particular cell is not found in the lookup  
> table, the
> function returns NA. I'm wondering how I can just ignore those  
> cells, and
> return the original contents if no match is found in the lookup table.
>
> Many thanks in advance, this site has been extremely helpful for me  
> so far,
> Jill
It's not clear to me just what you want to accomplish, but it's possible
that setting nomatch=0 in your call to match() might get you somewhere.

Note that xxx[c(0,1,2,3] gives xxx[c(1,2,3)] whereas
xxx[c(NA,1,2,3)] gives c(NA,xxx[c(1,2,3)]).

	cheers,

		Rolf Turner

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Let me clarify:
I'm using this--

dfnew<- sapply(df, function(df) lookuptable[match(df, lookuptable [ ,1]),
2])
>lookup
0101   01:01
0201   02:01
0301   03:01
0401   04:01
>df
0101   0301
0201   0401
0101   0502
>dfnew
01:01   03:01
02:01   04:01
01:01   NA

but what I want is:
>dfnew2
01:01   03:01
02:01   04:01
01:01   0502

thanks again,
Jill




Jill Hollenbach wrote:
> 
> Hi all,
> I think this is a very basic question, but I'm new to this so please
bear
> with me.
> 
> I'm using match to translate elements of a data frame using a lookup
> table. If the content of a particular cell is not found in the lookup
> table, the function returns NA. I'm wondering how I can just ignore
those
> cells, and return the original contents if no match is found in the lookup
> table.
> 
> Many thanks in advance, this site has been extremely helpful for me so
> far,
> Jill
> 
> Jill Hollenbach, PhD, MPH
>     Assistant Staff Scientist
>     Center for Genetics
>     Children's Hospital Oakland Research Institute
>     jhollenbach at chori.org
> 
-- 
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