[R] converting numerical parts of factors into numeric vectors

[Maria Wolters]

Dear list,

Problem:
Given a factor that contains both numerical values and category codes, 
how can I extract the numerical values and store them in a numeric 
vector while preserving the exact values? as.numeric() replaces the 
numerical values by their factor levels. But since the values represent
an interval-scaled distance measure, this is not exactly what is called
for. 

Current workaround: replace category codes by arbitrary numbers to be filtered
out later. In this case, negative numbers.

More elegant solution: ?

I checked CRAN, V&R, and the online help, but to no avail.

Thanks in advance for your help. (The problem is not urgent,
see "Current Workaround" ;)

Maria Wolters
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