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Re: st: Boxplots - avoiding the box in a strata with a small number of observations


From   Richard Hiscock <richardjhiscock@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Boxplots - avoiding the box in a strata with a small number of observations
Date   Tue, 4 Sep 2012 21:56:34 +1000

Thanks Nick for your help.
The last method will provide me with the detail I need
thanks Richard


On 4 Sep 2012, at 18:54, Nick Cox wrote:

> You can combine two or response variables with -by()- within -stripplot-.
> 
> stripplot Baseline Firstdose Thirddose , by(wtstrata, row(1)) box vertical
> 
> would be a start
> 
> On Tue, Sep 4, 2012 at 9:07 AM, Nick Cox <njcoxstata@gmail.com> wrote:
>> Allowing two or more -over()- options is characteristic only of -graph
>> box-, -graph dot-, -graph bar- etc. It is not possible in practice
>> with (a) -graph twoway- or (b) any command based on -twoway- such as
>> -dotplot- (although (b) at least is programmable).
>> 
>> -stripplot- (SSC) offers most if not of the flexibility you need. To
>> concoct a problem similar to yours, I typed
>> 
>> sysuse auto
>> gen himpg = mpg > 20
>> 
>> Then after some experimentation, this plot
>> 
>> stripplot weight , over(rep78) by(himpg) vertical box(barw(0.5)
>> blcolor(gs8))  width(100) center stack height(0.4)
>> 
>> seems adequate.
>> 
>> -stripplot- helps because
>> 
>> 1. Both -over()- and -by()- are supported, thus allowing two-way
>> classifications.
>> 
>> 2. If a group contains only one value, the box would be a bar of zero
>> length, which Stata won't (can't) show visibly.
>> 
>> 3. You can adjust the box colour to play down the boxes while keeping
>> them visible. I think this is a good idea generally.
>> 
>> 4. You can tinker with bin width, spacing of points and box width
>> 
>> Nick
>> 
>> N.B. One stratum, two or more strata.
>> 
>> On Tue, Sep 4, 2012 at 1:37 AM, Richard Hiscock
>> <richardjhiscock@gmail.com> wrote:
>> 
>>> I have continuous data (plasma level of drug) in patients, who received a dose determined by body weight (in five strata), measured at three time points.
>>> Whilst the lower strata have 40+ patients the highest two levels the number of patients is very small n = 5 & 2.
>>> To graphically present the plasma levels I would prefer to show individual data points but using dotplots however the command doesn't seem to allow for over commands (with data now in the long form).
>>> 
>>> dotplot plasma_level , over(time) over(wtstrata)
>>> 
>>> I can achieve close to what I want using boxplots, however I feel that boxes for the strata  with 5 & 2 only observations is not appropriate. Is there anyway to have individual data points displayed for these strata? The command I'm using in Stata 12 is
>>> 
>>> gr box  Baseline Firstdose Thirddose , over(wtstrata)
>>> 
>>> Any help or other presentation suggestions would be much appreciated
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