[R] Sub- or superscript in factorial variable - possible?

[peter dalgaard]

On Sep 16, 2012, at 07:48 , David Winsemius wrote:

> 
> On Sep 15, 2012, at 7:15 PM, mcg wrote:
> 
>> Hello R-users,
>> 
>> I would like to use subscript in chemical formulas for the different treatments in a boxplot.
>> Fot title, xlab and ylab sub- and superscript is no problem, but for the different treatments of the following example I cannot get subscript.
>> 
>> Example:
>> weight <-  c(6,5,7,2,7,3,9,4,2,7,8,9,2,3,4,5)
>> treatments <- as.factor(rep(c('Control', 'P2O5','K2SO4','CaSO4'),4))
>> data <- data.frame(treatments,weight)
>> boxplot(data$weight~data$treatments)
>> 
>> If I apply expression(P[2]...) I get  "unimplemented type 'expression' in 'HashTableSetup' ".
>> If there is a solution for this in base graphics or ggplot please let me know.
>> 
> 
> ?plotmath
> boxplot(data$weight~data$treatments, xaxt="n")
> axis(1, 1:4, labels=expression(Control, P[2]*O[5], K[2]*SO[4], CaSO[4]) )
> 
> I will admit that the need for the "*"'s was not apparent to me until I used the initial example as a starting point and made incremental changes until I gotsuccess. So I am not suggesting that RTM should have been enough.

Just remember that plotmath is designed to handle math expressions like alpha+beta*x and the logic should follow. For the same reason, although it makes little or no visual difference, you really should say

labels=expression(Control, P[2]*O[5], K[2]*S*O[4], Ca*S*O[4])

(Plotmath as of now doesn't actually do anything about kerning and such, but TeX afficionados will know that $different$ is quite different from \textit{different}, the former not being a word but identical to $dif^2e^2rnt$)

-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
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Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com