# [R] SpreadLevelPlot for more than one factor

Ashim Kapoor ashimkapoor at gmail.com
Sun Jan 7 10:35:16 CET 2018

```Dear All,

I did this :

> v = wool:tension
> spreadLevelPlot(breaks ~ v)
LowerHinge Median UpperHinge Hinge-Spread
B:H         15     17         21            6
A:M         18     21         30           12
A:H         18     24         28           10
B:M         21     28         39           18
B:L         20     29         31           11
A:L         26     51         54           28

Suggested power transformation:  -0.2756176

So the ans is approximately  = -.2

My query is:corresponding to  p , what is the corresponding power
transformation defined as? Is it x^p  or (x^p -1) / p ?

Which one of the following is the final transformation ? Please clarify.
> boxplot(breaks ^ -.2 ~v)
> boxplot((breaks^-.2 -1)/(-.2)~v)
>

Best Regards,
Ashim

On Sun, Jan 7, 2018 at 10:59 AM, Ashim Kapoor <ashimkapoor at gmail.com> wrote:

> Dear All,
>
> we need to do :
>
> library(car) for the spreadLevelPlot function
>
> I forgot to say that.
>
> Apologies,
> Ashim
>
> On Sun, Jan 7, 2018 at 10:37 AM, Ashim Kapoor <ashimkapoor at gmail.com>
> wrote:
>
>> 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
>>
>
>

[[alternative HTML version deleted]]

```

More information about the R-help mailing list