[R] SpreadLevelPlot for more than one factor

[Ashim Kapoor]

Dear All,

I want a transformation which will make the spread of the response at  all
combinations
of  2 factors the same.

See for example :

boxplot(breaks ~ tension * wool, warpbreaks)

The closest I  can do is :

spreadLevelPlot(breaks ~tension , warpbreaks)
spreadLevelPlot(breaks ~ wool , warpbreaks)

I want to do :

spreadLevelPlot(breaks ~tension * wool, warpbreaks)

But I get :

> spreadLevelPlot(breaks ~tension * wool , warpbreaks)
Error in spreadLevelPlot.formula(breaks ~ tension * wool, warpbreaks) :
  right-hand side of model has more than one variable

What is the corresponding appropriate function for 2 factors ?

Many thanks,
Ashim

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