Align boxplot and line graph

[Wouter Wakker]

Dear Statalisters,

I'm trying to combine a line graph with a boxplot in one row. The axes have the same scale, so I would like them to align nicely. However, the ycommon option doesn't work for boxplots and twoway graphs. Is there another way to align them?

* Example generated by -dataex-. To install: ssc install dataex
clear
input long incgroup_th int year double ka
1 1995  .6523464458247067
1 1996  .6502027260179435
1 1997  .5948507180650038
1 1998  .5661706349206348
1 1999   .582459372637944
1 2000  .5714285714285715
1 2001  .5798826777087647
1 2002  .6030803571428571
1 2003  .5980456349206349
1 2004  .6040013227513229
1 2005  .5784288194444445
1 2006  .5796006944444444
1 2007  .5569878472222222
1 2008  .5958333333333333
1 2009  .6405864197530865
1 2010  .6405864197530864
1 2011  .6378086419753086
1 2012             .69375
1 2013  .6939814814814814
1 2014  .6677777777777777
1 2015  .6677777777777777
1 2016  .6227777777777777
2 1995  .5054783950617284
2 1996 .46535126396237514
2 1997  .4997170781893004
2 1998  .5056327160493828
2 1999  .4841880341880342
2 2000  .5118357487922706
2 2001  .5165509259259259
2 2002  .5051587301587303
2 2003 .48673469387755103
2 2004  .4671075837742504
2 2005  .5032480893592006
2 2006  .5015079365079366
2 2007  .5085231193926846
2 2008  .4891025641025642
2 2009  .5119658119658119
2 2010  .5190821256038647
2 2011  .5450231481481481
2 2012  .5047777777777778
2 2013  .5327546296296296
2 2014  .5484444444444443
2 2015              .5625
2 2016  .5543438208616779
3 1995  .4632330246913581
3 1996 .43595679012345673
3 1997  .4049382716049383
3 1998 .41666666666666674
3 1999  .4141447368421053
3 2000 .39093750000000005
3 2001  .3097587719298246
3 2002   .306140350877193
3 2003 .26715686274509803
3 2004 .33596491228070174
3 2005 .34047619047619054
3 2006 .34920634920634924
3 2007  .3791062801932367
3 2008 .45425000000000004
3 2009 .46924999999999994
3 2010 .46495535714285735
3 2011  .4469907407407407
3 2012  .5079861111111111
3 2013  .4829861111111111
3 2014 .49134615384615377
3 2015 .46249999999999997
3 2016            .496875
4 1995 .13322482638888888
4 1996 .14518229166666669
4 1997  .1890522875816993
4 1998 .16838235294117646
4 1999  .1654411764705882
4 2000 .15073529411764702
4 2001 .14264705882352938
4 2002 .13749999999999998
4 2003               .145
4 2004  .1173611111111111
4 2005  .1527777777777778
4 2006 .15460526315789477
4 2007 .16052631578947368
4 2008 .15999999999999998
4 2009 .17006944444444444
4 2010  .1663194444444444
4 2011 .16506944444444444
4 2012 .17564599483204135
4 2013 .21306818181818182
4 2014 .21235795454545456
4 2015 .21511627906976752
4 2016 .20581395348837203
end
label values incgroup_th incomegroup5
label def incomegroup5 1 "Low Income", modify
label def incomegroup5 2 "Lower Middle Income", modify
label def incomegroup5 3 "Upper Middle Income", modify
label def incomegroup5 4 "High Income", modify

separate ka, by(incgroup_th) veryshortlabel
gen lastyear = ka if year == 2016
line ka? year, ylabel(0(0.2)1, format(%2.1g)) legend(off) xscale(range(2022)) || ///
scatter lastyear year, mlabel(incgroup_th) mcolor(none) name(line, replace)

graph box ka, over(incgroup_th, label(labsize(small))) name(box, replace) ylabel(0(0.2)1, format(%2.1g))

graph combine line box, iscale(0.5) ycommon

[Andrew Musau]

You have a title and ticks on the x-axis in the line graph, which causes the misalignment. I would do 2 things

1, Introduce a line break in the description of categories in the box plot, e.g.,

label def incomegroup5 1 `" "Low"   "Income" "', modify

2. Add ticks in the categorical axis of the box plot.

Without fully implementing 1, I get

label values incgroup_th incomegroup5
label def incomegroup5 1 `" "Low"   "Income" "', modify
label def incomegroup5 2 "Lower Middle Income", modify
label def incomegroup5 3 "Upper Middle Income", modify
label def incomegroup5 4 "High Income", modify

separate ka, by(incgroup_th) veryshortlabel
gen lastyear = ka if year == 2016
line ka? year, ylabel(0(0.2)1, format(%2.1g)) legend(off) xscale(range(2022)) || ///
scatter lastyear year, mlabel(incgroup_th) mcolor(none) name(line, replace)

graph box ka, over(incgroup_th, label(ticks))  name(box, replace) ylabel(0(0.2)1, format(%2.1g))

graph combine line box, iscale(0.5) ycommon

[Wouter Wakker]

Thanks Andrew, that's very helpful.

I didn't know you could break up labels, that's a nice trick. I also found that xscale(titlegap()) can be used to push the axis up and down a bit.

[Nick Cox]

Here's another take, using stripplot (SSC) to show dot-box plots.

separate ka, by(incgroup_th) veryshortlabel
gen lastyear = ka if year == 2016
line ka? year, ylabel(0(0.2)1, format(%2.1g)) legend(off) xscale(range(2022)) || ///
scatter lastyear year, mlabel(incgroup_th) mcolor(none) name(line, replace) xtitle("") ytitle(whatever makes sense) 

stripplot ka, over(incgroup_th) vertical name(box, replace) ylabel(0(0.2)1, format(%2.1g)) ///
box xtitle("") ytitle("") 

graph combine line box, iscale(0.5) ycommon

[Wouter Wakker]

Thank you Nick, that works nicely indeed.