Why my boxplot in Stata isn't showing whiskers?

[Mark Samoranos]

Good day! Please let me know how I can make the whiskers appear for my boxplot. I am just following tutorial on how to make boxplots in stata but when i try to generate my own, there are not any whiskers showing. I am new in exploring the use of Stata, none of the tutorials I found online seems to help. That is only my inquiry. I have attached a sample boxplot I am trying to make and it is not showing any whiskers. Thank you so much in advance.

[Rich Goldstein]

this sounds like a data issue; please read the FAQ and post your data using -dataex- and inside CODE blocks

[Mark Samoranos]

Hi Rich! thank you for your advise, could I show my data here as I only have a very small sample size which is this:

ID	sample a	sample b	sample c	sample d
1	0.0625	0.3125	0.3125	0.3125
1	0.0904	0.5578	0.2463	0.1055
1	0.0417	0.4545	0.3687	0.1352

I am only using Stata 13. So, when I try to make a boxplot with this data, I only generate the graphic I have attached in my earlier post. Thank you...

[Nick Cox]

In general, there can be no whiskers in the presence of ties such that 25% or more of values = maximum and 25% or more = minimum.

That has to be true also for a sample size of 3.

Just use a dotplot?

[Marcos Almeida]

this is not a problem related directly to Stata. That might be well the reason you didn't find tutorials on this particular situation.

But a fast Web-browsing will promptly reveal several texts on the subject.

Nick already clarified the issue, but you may wish to read this text, for example.

[Mark Samoranos]

I didn't know about that as I am only exploring the use of boxplots for data representation. Thank you very much for verifying it Nick, thank you as well Marcos. That text is indeed helpful

[Nick Cox]

There are also many posts on Cross Validated on box plots without whiskers. Another way to think about it is to push your data through summarize, detail or equivalently tabstat, which shows that Stata returns the same result for extremes and quartiles for this sample size.

clear 
input ID    sample_a    sample_b    sample_c    sample_d
1    0.0625    0.3125    0.3125    0.3125
1    0.0904    0.5578    0.2463    0.1055
1    0.0417    0.4545    0.3687    0.1352
end 

tabstat sample*, s(n min p25 p50 p75 max) c(stat)

    variable |         N       min       p25       p50       p75       max
-------------+------------------------------------------------------------
    sample_a |         3     .0417     .0417     .0625     .0904     .0904
    sample_b |         3     .3125     .3125     .4545     .5578     .5578
    sample_c |         3     .2463     .2463     .3125     .3687     .3687
    sample_d |         3     .1055     .1055     .1352     .3125     .3125
--------------------------------------------------------------------------

[Mark Samoranos]

Thanks so much Nick!

[Phil Bromiley]

Alternatively, it is not old enough to shave.