[R] Help for x axis

[Olivier]

Hi,
I want to customize x axis to scientific data. I do experiments with 
different triggers. As others publications, I want that there is one 
line for each trigger with the sign "-" or "+" to show if the trigger is 
used or no. You will find attached an exemple.
Please find below a data.frame you could use to explain me.
Thank you for your response,
Olivier



set.seed(3)
sampleData <- data.frame(id = 1:100,gender = sample(c("0", "1"), 100, 
replace = TRUE), smoke = sample (c("0","1"), 100, replace=TRUE), age = 
rnorm(100, 40, 10))
summary(sampleData)

-> I want to give results with histograms or box.plot (age according to 
sex and smoking status)
-> x axis may be like something like this :

Gender        -          -         +        +
Smoke         -          +        -         +

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