[R] ordering a boxplot

[Antonio Silva]

Thanks Bill and David

Here goes an example

SP1<-c(9,6,7,8,5,8,7,5,9,7)
SP2<-c(1,3,4,2,4,2,5,3,2,1)
SP3<-c(4,6,7,5,7,8,7,6,5,4)
SP4<-c(5,4,3,5,2,3,4,3,4,2)
mydata<-data.frame(SP1,SP2,SP3,SP4)
rownames(mydata)<-c("ST1","ST2","ST3","ST4","ST5","ST6","ST7","ST8","ST9","ST10")
mydata
boxplot(mydata)

Note that this data frame does not have the format Response ~ Group. In my
real matrix I have up to 40 species.

Is there any way to have the species ordered by their median abundance (or
other parameter?)

The desired order is given by names(sort(apply(mydata,2,median)))

Thanks once more,

Antonio Olinto
Fisheries Institute
Sao Paulo, Brazil

2015-03-21 15:13 GMT-03:00 William Dunlap <wdunlap em tibco.com>:

> You can use the reorder() function to reorder the grouping vector's
> factor levels according to a function of the data in each group.  E.g.,
> compare the following two plots:
>
>    d <- data.frame(Response=cos(1:15), Group=rep(c("A","B","C"),c(6,5,4)))
>    par(mfrow=c(1,2))
>    boxplot(Response ~ Group, data=d)
>    boxplot(Response ~ reorder(Group, X=Response, FUN=median), data=d)
>
>
> Bill Dunlap
> TIBCO Software
> wdunlap tibco.com
>
> On Fri, Mar 20, 2015 at 2:20 PM, Antonio Silva <aolinto.lst em gmail.com>
> wrote:
>
>> Hello
>>
>> I'm using a dataframe (mydata) where row names are sampling points and
>> column names are species in a multivariate analysis.
>>
>> If I write boxplot(mydata) I'll have boxplots for each species abundance
>> in
>> alphabetical order.
>>
>> How to get the boxes orderer by the median?
>>
>> Usually for this I write
>>
>> boxplot(value~category,at=rank(tapply(mydata$value,mydata$category,median)))
>> but for this to work I need a column for the categories and another column
>> for the values.
>>
>> Thanks in advance, best regards.
>>
>> Antonio Olinto
>>
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>>
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>
>

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