Extract Levels from a Factor in R

Question

I have got temperature data, which is stored as "factor", like this:

str(TEMPERATURE)
Factor w/ 2387 levels "-0.01","-0.02",..: 2285 2254 2256 2237 2217 2197 2175 
2162 2143 2143 ..

I use

TEMPERATURE<-as.numeric(TEMPERATURE)

Then, it becomes

str(TEMPERATURE)
num [1:39024] 2285 2254 2256 2237 2217 ...

I am wondering how to let it show real temperature, rather which levels the data belong to. Thanks.

score 1 · Accepted Answer · answered Jul 04 '16 at 18:53

Factors are stored internally as integers - specifically, indices in a lookup table. as.numeric extracts these integers, which is one of the amusing little quirks of R - this is almost never what someone will intend to do.

Convert first to character, then to numeric:

as.numeric(as.character(TEMPERATURE))

Extract Levels from a Factor in R

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