[R] replace matrix values with names from a dataframe
jhainm@fas.harvard.edu
jhainm at fas.harvard.edu
Thu Jul 28 15:52:29 CEST 2005
Hi,
I am looking for a way to replace matrix values with names from a dataframe.
Let me do this by example: I have a dataframe:
>data
city.name
1 munich
2 paris
3 tokio
4 london
5 boston
each city name corresponds to only one index number (there is only one
observation for each city). After doing some matching I end up with a matrix
that looks something like this:
> X
[,1] [,2]
[1,] 2 4
[2,] 5 1
[3,] 5 3
[4,] 12 217
[5,] 16 13
Here the numbers in the matrix are the index numbers from my original dataset,
each row is a matched pair (so e.g. the first row tells me that obs. number 2
(i.e. Paris) was matched to obs number 4 (i.e. London)).
Now I am looking for a quick way to transform the index numbers back to city
names, so that at the end I have a matrix that looks something like this:
> X.transformed
[,1] [,2]
[1,] paris london
[2,] boston munich
[3,] boston tokio
[4,] 12 217
[5,] 16 13
etc. So instead of the index number, the matrix should contain the names that
corresponds to it. In my real data, I have many many names and replacing each
value by hand would take too long. Any help is highly appreciated.
Thank you.
Regards,
Jens
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