for example I have data frame m as below:

m=as.data.frame(outer(1:5,6:9))
colnames(m)=c('a','b','c','d')

and I define the function

myf=function(df, colname){

   suppose colname is a, then:
   how can I get the column 'a'
   and how to get the colname as a string, 'a'

}

Thank you!

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