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Joining Dataframes

2 messages · Matt Goff, Don MacQueen

Original
Matt Goff
# 
I am attempting to join several dataframes that summarize sampling effort  
for different samples into one large data.frame/table.
I have looked at the merge command, but have not been clever enough to  
figure out how to get it to do what I want.

A simplified example of what I am trying to do:

The dataframes I have look like this (they were generated using the table  
command)

species1.effort
            site1   site2   site3
date1     5        5       5
date2     4        5       5
date3     4        5       5

species2.effort
            site1   site2   site3
date1     7        8        6
date3     8        7        8
date4     8        8        8

I would like to join these into a table that looks something like this:

Effort
             sp1.site1  sp1.site2  sp1.site3  sp2.site1  sp2.site2   
sp2.site2
date1         5               5          5             7              
8            6
date2         4               5          5            NA           
NA         NA
date3         4               5           5           8              
7             8
date4         NA           NA        NA         8            8              
8


I have many more dates and species, but I assume whatever method works for  
this small example, would work for larger cases.

Thanks,
Matt Goff
Don MacQueen
# 
It appears that you want to match rows by date. It also looks like 
your date information is in the row names, only, if the layout of 
your example can be trusted.

The help for merge says this:
     "By default the data frames are merged on the columns with names 
they both have..."
but the column you want to merge by, date, is not in either 
dataframe. So, obviously, it can't merge on date. Also, since your 
example has other columns with the same name that you do not want to 
merge on, you will have to tell it explicitly what columns to use for 
the merge.

So, assuming I've interpreted your example correctly, try this:
   (1) get your dates into a column
   (2) use the 'by' argument of merge to force it to merge on date only.

            merge(species1.effort, species2.effort, by='date')


-Don
At 11:37 AM -0800 10/4/05, Matt Goff wrote: