[R] Interquartile Range
Marc Schwartz
marc_schwartz at me.com
Wed Apr 20 02:24:17 CEST 2016
Hi,
Jumping into this thread mainly on the point of the mode of the distribution, while also supporting Bert's comments below on theory.
If the vector 'x' that is being passed to this function is an integer vector, then a tabulation of the integers can yield a 'mode', presuming of course that there is only one unique mode. You may have to decide how you want to handle a multi-modal discrete distribution.
If the vector 'x' is continuous (e.g. contains floating point values), then a tabulation is going to be problematic for a variety of reasons.
In that case, prior discussions on this point, have yielded the following estimation of the mode of a continuous distribution by using:
Mode <- function(x) {
D <- density(x)
D$x[which.max(D$y)]
}
where the second line of the function gets you the value of 'x' at the maximum of the density estimate. Of course, there is still the possibility of a multi-modal distribution and the nuances of which kernel is used, etc., etc.
Food for thought.
Regards,
Marc Schwartz
> On Apr 19, 2016, at 7:07 PM, Bert Gunter <bgunter.4567 at gmail.com> wrote:
>
> Well, instead of your functions try:
>
> Mode <- function(x) {
> tabx <- table(x)
> tabx[which.max(tabx)]
> }
>
> and use R's IQR function instead of yours.
>
> ... so I still don't get why you want to return a character string
> instead of a value for the IQR;
> and the mode of a sample defined as above is generally a bad estimator
> of the mode of the distribution. To say more than that would take me
> too far afield. Post on stats.stackexchange.com if you want to know
> why (if it's even relevant).
>
> Cheers,
> Bert
> Bert Gunter
>
> "The trouble with having an open mind is that people keep coming along
> and sticking things into it."
> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>
>
> On Tue, Apr 19, 2016 at 4:25 PM, Michael Artz <michaeleartz at gmail.com> wrote:
>> Hi,
>> Here is what I am doing
>>
>> notGroupedAll <- ddply(data
>> ,~groupColumn
>> ,summarise
>> ,col1_mean=mean(col1)
>> ,col2_mode=Mode(col2) #Function I wrote for getting the
>> mode shown below
>> ,col3_Range=myIqr(col3)
>> )
>>
>> groupedAll <- ddply(data
>> ,~groupColumn
>> ,summarise
>> ,col1_mean=mean(col1)
>> ,col2_mode=Mode(col2) #Function I wrote for getting the
>> mode shown below
>> ,col3_Range=Mode(col3)
>> )
>>
>> #custom Mode function
>> Mode <- function(x) {
>> ux <- unique(x)
>> ux[which.max(tabulate(match(x, ux)))]
>>
>> #the range function
>> myIqr <- function(x) {
>> paste(round(quantile(x,0.375),0),round(quantile(x,0.625),0),sep="-")
>> }
>>
>>
>> }
>>
>>
>> Here is what I am doing!! :)
>>
>>
>>
>> On Tue, Apr 19, 2016 at 2:57 PM, William Dunlap <wdunlap at tibco.com> wrote:
>>>
>>> If you show us, not just tell us about, a self-contained example
>>> someone might show you a non-hacky way of getting the job done.
>>> (I don't see an argument to plyr::ddply called 'transform'.)
>>>
>>> Bill Dunlap
>>> TIBCO Software
>>> wdunlap tibco.com
>>>
>>> On Tue, Apr 19, 2016 at 12:18 PM, Michael Artz <michaeleartz at gmail.com>
>>> wrote:
>>>>
>>>> Oh thanks for that clarification Bert! Hope you enjoyed your coffee! I
>>>> ended up just using the transform argument in the ddply function. It worked
>>>> and it repeated, then I called a mode function in another call to ddply that
>>>> summarised. Kinda hacky but oh well!
>>>>
>>>> On Tue, Apr 19, 2016 at 12:31 PM, Bert Gunter <bgunter.4567 at gmail.com>
>>>> wrote:
>>>>>
>>>>> ... and I'm getting another cup of coffee...
>>>>>
>>>>> -- Bert
>>>>> Bert Gunter
>>>>>
>>>>> "The trouble with having an open mind is that people keep coming along
>>>>> and sticking things into it."
>>>>> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>>>>>
>>>>>
>>>>> On Tue, Apr 19, 2016 at 10:30 AM, Bert Gunter <bgunter.4567 at gmail.com>
>>>>> wrote:
>>>>>> NO NO -- I am wrong! The paste() expression is of course evaluated.
>>>>>> It's just that a character string is returned of the form "something -
>>>>>> something".
>>>>>>
>>>>>> I apologize for the confusion.
>>>>>>
>>>>>> -- Bert
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> Bert Gunter
>>>>>>
>>>>>> "The trouble with having an open mind is that people keep coming along
>>>>>> and sticking things into it."
>>>>>> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>>>>>>
>>>>>>
>>>>>> On Tue, Apr 19, 2016 at 10:25 AM, Bert Gunter <bgunter.4567 at gmail.com>
>>>>>> wrote:
>>>>>>> To be precise:
>>>>>>>
>>>>>>> paste(round(quantile(x,0.25),0),round(quantile(x,0.75),0),sep="-")
>>>>>>>
>>>>>>> is an expression that evaluates to a character string:
>>>>>>> "round(quantile(x,.25),0) - round(quantile(x,0.75),0)"
>>>>>>>
>>>>>>> no matter what the argument of your function, x. Hence
>>>>>>>
>>>>>>> return(paste(...)) will return this exact character string and never
>>>>>>> evaluates x.
>>>>>>>
>>>>>>>
>>>>>>> Cheers,
>>>>>>> Bert
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Bert Gunter
>>>>>>>
>>>>>>> "The trouble with having an open mind is that people keep coming
>>>>>>> along
>>>>>>> and sticking things into it."
>>>>>>> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>>>>>>>
>>>>>>>
>>>>>>> On Tue, Apr 19, 2016 at 8:34 AM, William Dunlap via R-help
>>>>>>> <r-help at r-project.org> wrote:
>>>>>>>>> That didn't work Jim!
>>>>>>>>
>>>>>>>> It always helps to say how the suggestion did not work. Jim's
>>>>>>>> function had a typo in it - was that the problem? Or did you not
>>>>>>>> change the call to ddply to use that function. Here is something
>>>>>>>> that might "work" for you:
>>>>>>>>
>>>>>>>> library(plyr)
>>>>>>>>
>>>>>>>> data <- data.frame(groupColumn=rep(1:5,1:5), col1=2^(0:14))
>>>>>>>> myIqr <- function(x) {
>>>>>>>>
>>>>>>>> paste(round(quantile(x,0.25),0),round(quantile(x,0.75),0),sep="-")
>>>>>>>> }
>>>>>>>> ddply(data, ~groupColumn, summarise, col1_myIqr=myIqr(col1),
>>>>>>>> col1_IQR=stats::IQR(col1))
>>>>>>>> # groupColumn col1_myIqr col1_IQR
>>>>>>>> #1 1 1-1 0
>>>>>>>> #2 2 2-4 1
>>>>>>>> #3 3 12-24 12
>>>>>>>> #4 4 112-320 208
>>>>>>>> #5 5 2048-8192 6144
>>>>>>>>
>>>>>>>> The important point is that
>>>>>>>>
>>>>>>>> paste(round(quantile(x,0.25),0),round(quantile(x,0.75),0),sep="-")
>>>>>>>> is not a function, it is an expression. ddplyr wants functions.
>>>>>>>>
>>>>>>>>
>>>>>>>> Bill Dunlap
>>>>>>>> TIBCO Software
>>>>>>>> wdunlap tibco.com
>>>>>>>>
>>>>>>>> On Tue, Apr 19, 2016 at 7:56 AM, Michael Artz
>>>>>>>> <michaeleartz at gmail.com>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> That didn't work Jim!
>>>>>>>>>
>>>>>>>>> Thanks anyway
>>>>>>>>>
>>>>>>>>> On Mon, Apr 18, 2016 at 9:02 PM, Jim Lemon <drjimlemon at gmail.com>
>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>> Hi Michael,
>>>>>>>>>> At a guess, try this:
>>>>>>>>>>
>>>>>>>>>> iqr<-function(x) {
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> return(paste(round(quantile(x,0.25),0),round(quantile(x,0.75),0),sep="-")
>>>>>>>>>> }
>>>>>>>>>>
>>>>>>>>>> .col3_Range=iqr(datat$tenure)
>>>>>>>>>>
>>>>>>>>>> Jim
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On Tue, Apr 19, 2016 at 11:15 AM, Michael Artz
>>>>>>>>>> <michaeleartz at gmail.com>
>>>>>>>>>> wrote:
>>>>>>>>>>> Hi,
>>>>>>>>>>> I am trying to show an interquartile range while grouping
>>>>>>>>>>> values
>>>>>>>>> using
>>>>>>>>>>> the function ddply(). So my function call now is like
>>>>>>>>>>>
>>>>>>>>>>> groupedAll <- ddply(data
>>>>>>>>>>> ,~groupColumn
>>>>>>>>>>> ,summarise
>>>>>>>>>>> ,col1_mean=mean(col1)
>>>>>>>>>>> ,col2_mode=Mode(col2) #Function I wrote for
>>>>>>>>>>> getting
>>>>>>>>> the
>>>>>>>>>>> mode shown below
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> ,col3_Range=paste(as.character(round(quantile(datat$tenure,c(.25)))),
>>>>>>>>>>> as.character(round(quantile(data$tenure,c(.75)))), sep = "-")
>>>>>>>>>>> )
>>>>>>>>>>>
>>>>>>>>>>> #custom Mode function
>>>>>>>>>>> Mode <- function(x) {
>>>>>>>>>>> ux <- unique(x)
>>>>>>>>>>> ux[which.max(tabulate(match(x, ux)))]
>>>>>>>>>>> }
>>>>>>>>>>>
>>>>>>>>>>> I am not sre what is going wrong on my interquartile range
>>>>>>>>>>> function, it
>>>>>>>>>>> works on its own outside of ddply()
>>>>>>>>>>>
>>>>>>>>>>> [[alternative HTML version deleted]]
>>>>>>>>>>>
>>>>>>>>>>> ______________________________________________
>>>>>>>>>>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more,
>>>>>>>>>>> see
>>>>>>>>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>>>>>>>>> PLEASE do read the posting guide
>>>>>>>>>> http://www.R-project.org/posting-guide.html
>>>>>>>>>>> and provide commented, minimal, self-contained, reproducible
>>>>>>>>>>> code.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> [[alternative HTML version deleted]]
>>>>>>>>>
>>>>>>>>> ______________________________________________
>>>>>>>>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>>>>>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>>>>>>> PLEASE do read the posting guide
>>>>>>>>> http://www.R-project.org/posting-guide.html
>>>>>>>>> and provide commented, minimal, self-contained, reproducible code.
>>>>>>>>>
>>>>>>>>
>>>>>>>> [[alternative HTML version deleted]]
>>>>>>>>
>>>>>>>> ______________________________________________
>>>>>>>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>>>>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>>>>>> PLEASE do read the posting guide
>>>>>>>> http://www.R-project.org/posting-guide.html
>>>>>>>> and provide commented, minimal, self-contained, reproducible code.
>>>>
>>>>
>>>
>>
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
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