[R] matching and extracting data

[David Winsemius]

On Nov 27, 2009, at 10:25 AM, ram basnet wrote:

> Dear all,
> I have querry on how to extract the data by matching between two  
> data set where one has the same elements multiple times?
>
> For example, I have two matrix X and Y.
>> X
>    [,1]    [,2]       [,3]
> 1  A     5          P
> 2  B      6         P
> 3  C     7         P
> 4  D     5         Q
> 5  E      6         Q
> 6  F      7         Q
> 7  G     5          R
> 8  H     6          R
> 9  I       7          S
> 10 J      5         S
> 11 K    6          T
> 12 L     7          T
>
> and
>
>> Y       [,1]
> 1          P
> 2          Q
> 3          R
> 4          S
>
> Now, I want to select and extract all the data of P, Q, R and S  
> elements of column 3 of X matrix by matching with column 1 of Y  
> matrix like below:
>
>> [,1]   [,2]       [,3]
> 1  A     5          P
> 2  B      6         P
> 3  C     7         P
> 4  D     5         Q
> 5  E      6         Q
> 6  F      7         Q
> 7  G     5          R
> 8  H     6          R
> 9  I       7          S
> 10 J      5         S

Perhaps (untested):

X[ X[,3] %in% Y[,1] , ]

Would have been tested if you had used dput or dump on your matrices.

-- 
David.

>
> I guess, the answer might be simple but i am not getting way to  
> figure out. And, i have to select subset from very huge data set.  
> So, i need some kinds of automated procedure.
> If some one can help me, it will be great
>
> Thanks in advance.
>
> Sincerely,
> Ram Kumar Basnet
>
>
>
>
> 	[[alternative HTML version deleted]]
>
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT