[R] Opinion: Why I find factors convenient to use

[Jeff Newmiller]

I don't know if my recent post on this prompted your post, but I don't see much to argue with in your discussion. I find factors to be useful for managing display and some kinds of analysis.  

However, I find them mostly a handicap when importing, merging, and handling data QC. Therefore I delay conversion until late in the game... but usually I do eventually convert in most cases.
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Sent from my phone. Please excuse my brevity.



Bert Gunter <gunter.berton at gene.com> wrote:

>Folks:
>
>Over the years, many people -- including some who I would consider
>real expeRts -- have criticized factors and advocated the use
>(sometimes exclusively) of character vectors instead. I would just
>like to point out that, for me, factors provide one feature that I
>find to be very convenient: ordering of levels. **
>
>As an example, suppose one has a character vector of labels "small,"
>medium", and "large". Then most R functions (e.g. tapply()) will
>display results involving this vector in alphabetical order, which I
>think most would view as undesirable. By converting to a factor with
>levels in the logical order, displays will automatically be "logical."
>For example:
>
>> x <- sample(c("small","medium","large"),12,rep=TRUE)
>> table(x)
>x
> large medium  small
>     2      3      7
>> y <- factor(x,lev=c("small","medium","large")) ##ordered() also would
>do, but is not necessary for this
>> table(y)
>y
> small medium  large
>     7      3      2
>
>Naturally, this is just my opinion, and I understand why lots of smart
>people find factors irritating (at least!). So contrary opinions
>cheerily welcomed. But perhaps these comments might be helpful to
>those who have been "bitten" by factors or just wonder what all the
>fuss is about.
>
>** Another advantage is reduced storage space, I believe. Please
>correct if wrong.
>
>Cheers,
>Bert
>
>-- 
>
>Bert Gunter
>Genentech Nonclinical Biostatistics
>
>Internal Contact Info:
>Phone: 467-7374
>Website:
>http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm
>
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