[R] Linking 2 columns in 2 databases and applying a function

[B77S]

1st of all Dr Utz, thanks for your recent pubs on regional differences
between the piedmont and coastal plain streams.  

and to add to Daniels post (giving your binary yes/no):

df<-merge(x,y,all.x=T,all.y=F)

df["exceed"] <- ifelse(df$Q>df$Threshold_Q , 1, 0)

## now look at df
df





Daniel Malter wrote:
> 
> For example, you can merge the two data frames and do a direct comparison:
> 
> df<-merge(x,y,all.x=T,all.y=F)
> df
> df$Q>df$Threshold_Q
> 
> HTH,
> Daniel 
> 
> 
> Ryan Utz-2 wrote:
>> 
>> Hi all,
>> 
>> I have two datasets, one that represents a long-term time series and one
>> that represents summary data for the time series. It looks something like
>> this:
>> 
>> x<-data.frame(Year=c(2001,2001,2001,2001,2001,2001,2002,2002,2002,2002,2002,2002),
>> Month=c(1,1,1,2,2,2),Q=c(5,5,5,6,6,6,3,3,3,4,4,5))
>> y<-data.frame(Year=c(2001,2001,2002,2002),Month=c(1,2,1,2),Threshold_Q=c(5,5,4,4))
>> 
>> What I'd like to do is link the Year and Month fields in both dataframes
>> then determine if Q exceeds Q_Threshold (by noting it with something like
>> 1
>> or 0 in a new field in the dataframe x).
>> 
>> If I were doing this in the more-familiar-to-me Matlab, I'd just write a
>> pair of nested for-loops. But as we know, this won't fly in R. I've tried
>> reading the help pages and seeking for solutions on the net, with no luck
>> (I'm relatively new to R and the help pages are still a bit opaque to
>> me).
>> It seems like the functions "apply" or "lapply" are key, but I can't make
>> sense of their syntax.
>> 
>> Any advice/help?!?
>> 
>> Many thanks,
>> Ryan
>> 
>> -- 
>> 
>> Ryan Utz, Ph.D.
>> Aquatic Ecologist/STREON Scientist
>> National Ecological Observatory Network
>> 
>> Home/Cell: (724) 272-7769
>> Work: (720) 746-4844 ext. 2488
>> 
>> 	[[alternative HTML version deleted]]
>> 
>> ______________________________________________
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>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>> 
> 

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