[R] a complicated merging task

I would like to merge two dataframes, but i have a condition that needs to used for the merge as well. the rows (observations) in each dataframe are identified by each person's ID and by the date of the observation. Basically I would like it to be merged based on both ID (exact match) and date

Re: [R] matching each row

best try so far is to do: tempA <- aggregate(dataA$unique.id,list(dataA$unique.id),length) which gives me a matrix with ONE instance of each unique.id and the counts... (and which I thought was kinda cute) but it only works for within a single dataset! tathta wrote: > > I have t

Re: [R] matching each row

Close... The output I'm looking for is more like this: output <- data.frame(unique.id=c(1,3,5,7,9),N.in.x=c(2,3,1,2,1),N.in.y=c(0,1,3,1,1)) The first column can be gotten using a small change to the first table line: table ( x [ which ( x %in% x ) ] ) ##the 3rd "x" used to be a "y" but

[R] matching each row

I have two dataframes, the first column of each dataframe is a unique id number (the rest of the columns are data variables). I would like to figure out how many times each id number appears in each dataframe. So far I can use: length( match (dataframeA$unique.id[1], dataframeB$unique.id) )