[R] how to not match partial names

[Tóth Dénes]

> Dear friends,
>
> How do I stop partial matching of list names?
>
> e.g.,
>
> x <- list(AAAA="aaaaa", BBBBB="bbbbb")
> is.null(x$A)   #returns FALSE  even though there is no element A.
>
> if(is.null(x$A))  {result <-  x$BBBB} else {result <- x$A}
> result   #is aaaa even though there is no x$A element
>
> x <- list(CCCC="aaaaa", BBBBB="bbbbb")
> if(is.null(x$A))  {result <-  x$BBBB} else {result <- x$A}
> result   #this is great
>
> x <- list(ABC="aaaaa", BBBBB="bbbbb")
> if(is.null(x$A))  {result <-  x$BBBB} else {result <- x$A}
> result  #partial matches  and returns aaaa
>
> x <- list(ABC="abc", BBBBB="bbbbb",AA="aaaa")
> if(is.null(x$A))  {result <-  x$BBBB} else {result <- x$A}
> result  #can not partial match, and thus returns bbbb
>
> x <- list(AAB="aab", BBBBB="bbbbb",AA="aaaa")
> if(is.null(x$A))  {result <-  x$BBBB} else {result <- x$A}
> result #also can not partial match
>
> My need for this is that I have several functions that return lists
> and I am trying to extract AAAA if it exists, but something else if
> it does not.


ifelse("AAAA" %in% names(x),x[["AAAA"]],x[["BBBB"]])


HTH,
  Denes


>
> Thanks.
>
> Bill
>
> --
> William Revelle		http://personality-project.org/revelle.html
> Professor			http://personality-project.org
> Department of Psychology
> http://www.wcas.northwestern.edu/psych/
> Northwestern University	http://www.northwestern.edu/
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