RE: statalist-digest V4 #4961: Re: st: Value labels won't show on box plot axis

["Allan Reese (Cefas)" <allan.reese@cefas.co.uk>]

On 1 August 2013 10:46, Walsh, Lee <l.walsh@ucl.ac.uk> wrote:
>> I am box plotting a variable grouped by another.  
>> I am telling stata to use the value labels for the y axis 
>> but it insists on showing the numerical values.  
>>
>> graph box response, over(statementNum) ylabel(1(1)7, valuelabel) 

On 1 Aug 2013 11:00:00 +0100, Nick Cox <njcoxstata@gmail.com> agreed
> This didn't work either in my experiments. Here's a replicable example
> and a work-around:

> . sysuse auto
> . graph box foreign, over(rep78) yla(0 1, valuelabel)
 
[and built a list of re-labels in a macro named -call-] 
...
> forval i = 1/7 {
>       local call `call' `i' "`: label (response) `i''"
> }
[which was then used in the -graph- command]
 . graph box response, over(statementNum) yla(`call')
-------------------------------------------------------

That's an elegant and general piece of programming, but ignores the semantic question of why you would use a boxplot on a non-metric variable.  I take it that Lee's responses are a 7-point opinion scale. There are differing views on whether it is valid to compare means of scales, given the numeric codes are arbitrary beyond the ordering.  Extracting the five-number summary and making a boxplot seems very doubtful to me. Nick's cars example plot shows the effect of applying boxplots to a discrete variable with few values and multiple coincidences.

It may be quicker and less baffling for small numbers of re-labels to write the code explicitly.  I've recently had numerous graphs where a particular value represents the "limit of detection".  That is certainly worth drawing attention to in the graph rather than just in the caption.  I also prefer natural labels when plotting a logged number.  Bacterial counts usually follow a lognormal distribution.

graph box logbact, over(groupvar) ylab(1.3 "20=LoD" 2 "100" 3 "1000" ...)  

Allan
    



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