> On Jul 15, 2017, at 4:01 AM, Andras Farkas via R-help <[email protected]>
> wrote:
>
> Dear All,
>
> wonder if you could please assist with the following
>
> df<-data.frame(ID=c(1,1,1,2,2,3,3,4,4,5,5),samples=c("A","B","C","A","C","A","D","C","B","A","C"))
>
> from this data frame the goal is to extract the value of 3 from the ID column
> based on the logic that the ID=3 in the data frame has NO row that would pair
> 3 with either "B", AND/OR "C" in the samples column...
>
This returns a vector that determines if either of those characters are in the
character values of that factor column you created. Coercing to character is
needed because leaving samples as a factor generated an invalid factor level
warning and gave useless results.
with( df, ave( as.character(samples), ID, FUN=function(x) {!any(x %in%
c("B","C"))}))
[1] "FALSE" "FALSE" "FALSE" "FALSE" "FALSE" "TRUE" "TRUE" "FALSE" "FALSE"
[10] "FALSE" "FALSE"
You can then use it to extract and consolidate to a single value (although
wrapping with as.logical was needed because `ave` returned character class
values):
unique( df$ID[ as.logical( # fails without this since "FALSE" != FALSE
with( df,
ave( as.character(samples), ID, FUN=function(x) {!any(x
%in% c("B","C"))})))
] )
#[1] 3
The same sort of logic could also be constructed with a for-loop:
> for (x in unique(df$ID) ) { if ( !any( df$samples[df$ID==x] %in% c("b","C"))
> ) print(x) }
[1] 3
Although you are warned that for-loops do not return values and you might need
to make an assignment rather than just printing.
--
David Winsemius
Alameda, CA, USA
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