R: Convert variable name to string in sapply

Question

I have found that to convert a variable name into a string I would use deparse(substitute(x)) where x is my variable name. But what if I want to do this in an sapply function call?

sapply( myDF, function(x) { hist( x, main=VariableNameAsString ) } )

When I use deparse(substitute(x)), I get something like X[[1L]] as the title. I would like to have the actual variable name. Any help would be appreciated.

David

Answer 1

If you need the names, then iterate over the names, not the values:

sapply(names(myDF), function(nm) hist(myDF[[nm]], main=nm))

Alternatively, iterate over both names and values at the same time using mapply or Map:

Map(function(name, values) hist(values, main=name),
    names(myDF), myDF)

For the most part, you shouldn't be using deparse and substitute unless you are doing metaprogramming (if you don't know what it is, you're not doing it).