R help - Sep 2015 - finding those elements of listA that are found in listB

I have two structures. I think they are lists, but I am not sure. Both
structures contain integers. I am trying to find those members of list b that
are found in list a. I have tried to perform the search using grep, but I get an
error. Please see code below. I would appreciate knowing how to search listB for
any element in listA
Thanks
John

> str(listA)
 int [1:42] 13083 13705 14123 14168 14382 14652 14654 14678 14817 14822
...
> str(listB)
 int [1:633] 13083 13083 13083 13083 13083 13083 13705 13705 13705 13705
...
> grep(listA,listB)
[1] 1 2 3 4 5 6
Warning message:
In grep(listA, listB) :
  argument 'pattern' has length > 1 and only the first element will
be used







 

John David Sorkin M.D., Ph.D.
Professor of Medicine
Chief, Biostatistics and Informatics
University of Maryland School of Medicine Division of Gerontology and Geriatric
Medicine
Baltimore VA Medical Center
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524
(Phone) 410-605-7119
(Fax) 410-605-7913 (Please call phone number above prior to faxing) 


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I think you are looking for match or %in% (which is a based on match)
> a <- sample(12)
> b <- c(1, 3, 5, 11, 17)
> a
 [1] 10  8  1  4  7  3  6 11  2 12  5  9
> b
[1]  1  3  5 11 17
> [1] 1
> match(a, b)
 [1] NA NA  1 NA NA  2 NA  4 NA NA  3 NA
> match(a, b, 0)
 [1] 0 0 1 0 0 2 0 4 0 0 3 0
> match(b, a)
[1]  3  6 11  8 NA
> match(b, a, 0)
[1]  3  6 11  8  0
> a %in% b
 [1] FALSE FALSE  TRUE FALSE FALSE  TRUE FALSE  TRUE FALSE FALSE  TRUE
FALSE
> b %in% a
[1]  TRUE  TRUE  TRUE  TRUE FALSE
>
Rich

On Wed, Sep 16, 2015 at 10:43 PM, John Sorkin <JSorkin at
grecc.umaryland.edu>
wrote:
> I have two structures. I think they are lists, but I am not sure. Both
> structures contain integers. I am trying to find those members of list b
> that are found in list a. I have tried to perform the search using grep,
> but I get an error. Please see code below. I would appreciate knowing how
> to search listB for any element in listA
> Thanks
> John
>
>
> > str(listA)
>  int [1:42] 13083 13705 14123 14168 14382 14652 14654 14678 14817 14822 ...
> > str(listB)
>  int [1:633] 13083 13083 13083 13083 13083 13083 13705 13705 13705 13705
> ...
> > grep(listA,listB)
> [1] 1 2 3 4 5 6
> Warning message:
> In grep(listA, listB) :
>   argument 'pattern' has length > 1 and only the first element
will be used
>
>
>
>
>
>
>
>
>
> John David Sorkin M.D., Ph.D.
> Professor of Medicine
> Chief, Biostatistics and Informatics
> University of Maryland School of Medicine Division of Gerontology and
> Geriatric Medicine
> Baltimore VA Medical Center
> 10 North Greene Street
> GRECC (BT/18/GR)
> Baltimore, MD 21201-1524
> (Phone) 410-605-7119
> (Fax) 410-605-7913 (Please call phone number above prior to faxing)
>
>
> Confidentiality Statement:
> This email message, including any attachments, is for ...{{dropped:16}}

John,

The intersect() function may help you.  For example:

listA <- sort(sample(10, 5))
listB <- sort(sample(10, 5))
both <- intersect(listA, listB)
> listA
[1] 2 4 7 8 9
> listB
[1]  1  2  3  8 10
> both
[1] 2 8

Jean

On Wed, Sep 16, 2015 at 9:43 PM, John Sorkin <JSorkin at
grecc.umaryland.edu>
wrote:
> I have two structures. I think they are lists, but I am not sure. Both
> structures contain integers. I am trying to find those members of list b
> that are found in list a. I have tried to perform the search using grep,
> but I get an error. Please see code below. I would appreciate knowing how
> to search listB for any element in listA
> Thanks
> John
>
>
> > str(listA)
>  int [1:42] 13083 13705 14123 14168 14382 14652 14654 14678 14817 14822 ...
> > str(listB)
>  int [1:633] 13083 13083 13083 13083 13083 13083 13705 13705 13705 13705
> ...
> > grep(listA,listB)
> [1] 1 2 3 4 5 6
> Warning message:
> In grep(listA, listB) :
>   argument 'pattern' has length > 1 and only the first element
will be used
>
>
>
>
>
>
>
>
>
> John David Sorkin M.D., Ph.D.
> Professor of Medicine
> Chief, Biostatistics and Informatics
> University of Maryland School of Medicine Division of Gerontology and
> Geriatric Medicine
> Baltimore VA Medical Center
> 10 North Greene Street
> GRECC (BT/18/GR)
> Baltimore, MD 21201-1524
> (Phone) 410-605-7119
> (Fax) 410-605-7913 (Please call phone number above prior to faxing)
>
>
> Confidentiality Statement:
> This email message, including any attachments, is for ...{{dropped:16}}