[R] Problems with merge

TEMPL Matthias Matthias.Templ at statistik.gv.at
Wed Oct 6 08:31:09 CEST 2004


You can change e.g. the second column name in the following way:

[1] "Sepal.Length" "Sepal.Width"  "Petal.Length" "Petal.Width"

To change the second column name:

colnames(iris)[2] <- "name"
[1] "Sepal.Length" "name"         "Petal.Length" "Petal.Width"


> This issue has been discussed on this list before but the solutions 
> offerred are not satisfactory. So I thought I shall raise it again.
> I want to merge two datasets which have three common variables. These 
> variables DO NOT have the same names in both the files. In addition, 
> there are two variables with same name which do not necessarily have 
> exactly same data. That is, there could be some discrepancy 
> between the 
> two datasets when it comes to these variables. I do not want 
> them to be 
> used when I merge the datasets.
> The problem is that R allows you to use by.x and by.y variables to 
> specify only one variable in x dataset and one variable in y 
> dataset to 
> merge. Otherwise, if you do not specify anything, it matches all the 
> variables that have common names to merge. This is very 
> problemmatic. In 
> my case, the variables I want to use to match do not have 
> same names in 
> two datasets and the ones that have same names must not be 
> used to match.
> One approach will be to change names of variables and then merge. But 
> that is not elegant, to say the least.
> If nothing else works, that is what I shall have to do. There 
> again we 
> have some problem. How do I change the name of a particular 
> column. One 
> solution suggested somewhere in the archives of the list is to use
> names(data.frame)=c(list of column names)
> But this requires you to list all the variable names. That 
> can obviously 
> be cumbersome when you have large number of variables. What 
> would be the 
> syntax if I want to change just one column name.
> Vikas
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