Hi Statalist,

Using 'graph combine' I have combined four graphs. The graphs depict physiological data (oxygen saturation, heart rate, sleep stage, and body position) simultaneously recorded over one night. For ease with interpretation, all the times on the x-axes must align vertically. I have used 'xcommon', which I assume scales the x-axes with a common range. However, the x-axes of the graphs still do not align, as the label sizes of the y-axes differ.

How can I combine the four graphs so that the x-axes perfectly align, and not just have a common range?

Thanks so much, as always.

Generate example data (thought this would be easier than 'dataex').
Code:
clear
insobs 100
egen datetime = seq()
gen spo2 = runiformint(80,100)
gen hr = runiformint(50,110)
gen ss = runiformint(0,4)
gen bp = runiformint(0,6)
Draw the four graphs and combine them. This is the original code, except I made some changes to accommodate the example data.
Code:
twoway ///
    (line spo2 datetime, lcolor("18 22 70%100") lwidth(vthin) xaxis(1) cmissing(n)), ///
    yscale(range(60 100)) ///
    ytitle("SpO2 (%)", axis(1) size(small)) /// xtitle(, axis(2) color(%0) size(zero)) ///xtitle(, axis(1) color(%0) size(zero)) ///
    graphregion(lwidth(none) ilwidth(none) lcolor(none) fcolor(white)) ///
    plotregion(fcolor(white) lcolor(white) lwidth(none) ilwidth(none) margin(zero)) ///
    xlabel(0 (10) 100, grid axis(1) format(%tcHH:MM) labsize(small) labcolor(black%100)) ///    
    ylabel(60(10)100, angle(horizontal)) ///
    yline(88, lpattern(shortdash) lwidth(vthin) lcolor("255 20 66")) ///
    xtitle(, axis(1) color(%0) size(zero)) ///
    legend(off) ///
    xsize(7.09) ///   
    ysize(1.15) ///
    nodraw ///
    name("oxygen_graph", replace)

twoway ///
    (line hr datetime, lcolor("18 22 70%100") lwidth(vthin) xaxis(1) cmissing(n)), ///
    ytitle("Heart rate (bpm)", axis(1) size(small)) ///xtitle(, axis(2) color(%0) size(zero)) ///xtitle(, axis(1) color(%0) size(zero)) ///
    graphregion(lwidth(none) ilwidth(none) fcolor(white) lcolor(white)) ///
    plotregion(fcolor(white) lcolor(black) lwidth(none) ilwidth(none) margin(zero)) ///
    xlabel(0 (10) 100, grid axis(1) format(%tcHH:MM) labsize(small) labcolor(black%100)) ///    
    ylabel(, angle(horizontal)) ///
    xtitle(, axis(1) color(%0) size(zero)) ///
    legend(off) ///
    xsize(7.09) ///   
    ysize(1.15) ///
    nodraw ///
    name("hr_graph", replace)
    
twoway ///
    (area ss datetime, fcolor("18 22 70%100") lwidth(none) base(0)), ///
    yscale(reverse) ///
    ytitle("Sleep stage", axis(1) size(small)) ///xtitle(, axis(2) color(%0) size(zero)) ///xtitle(, axis(1) color(%0) size(zero)) ///
    graphregion(lwidth(none) lcolor(none) ilwidth(none) fcolor(white)) ///
    plotregion(fcolor(white) lcolor(black) lwidth(none) ilwidth(none) margin(zero)) ///
    xlabel(0 (10) 100, grid axis(1) format(%tcHH:MM) labsize(small) labcolor(black%100)) ///    
    ylabel(0.5 "W" 1.5 "R" 2.5 "L" 3.5 "D", noticks nogrid angle(horizontal)) ///
    xtitle(, axis(1) color(%0) size(zero)) ///
    legend(off) ///
    xsize(7.09) ///   
    ysize(3.15) ///
    nodraw ///
    name("hypnogram_graph", replace)

twoway ///
    (area bp datetime, fcolor("255 20 66%100") lwidth(none) base(0)) ///
    ,yscale(range(0(1)7) reverse) ///
    ytitle("Body position", axis(1) size(small)) ///xtitle(, axis(2) color(%0) size(zero)) ///xtitle(, axis(1) color(%0) size(zero)) ///
    graphregion(lwidth(none) lcolor(none) ilwidth(none) fcolor(white)) ///
    plotregion(fcolor(white) lcolor(black) lwidth(none) ilwidth(none) margin(zero)) ///
    xlabel(0 (10) 100, grid axis(1) format(%tcHH:MM) labsize(small) labcolor(black%100)) ///    
    ylabel(0.5 "in motion" 1.5 "upright" 2.5 "inclined" 3.5 "supine" 4.5 "left side" 5.5 "right side" 6.5 "prone", noticks nogrid angle(horizontal)) ///
    xtitle(, axis(1) color(%0) size(zero)) ///
    legend(off) ///
    xsize(7.09) ///   
    ysize(3.15) ///
    nodraw ///
    name("bodyposition_graph", replace)
    
graph combine ///
    oxygen_graph hr_graph hypnogram_graph bodyposition_graph, ///
    xcommon ///
    cols(1) ///
    graphregion(fcolor(white) lcolor(white) lwidth(none) ilwidth(none) margin(zero)) ///
    plotregion(fcolor(white) lcolor(black) lwidth(none) ilwidth(none) margin(vsmall)) ///
    imargin(zero) ///
    name(oxygen_hr_hypnogram, replace)