Problems with creating splines using xblc

[Sigrid Vikjord]

Dear Statalist,

I have a problem with a syntax I have used several times before. I'm trying to plot BMI values against HR using splines, and I'm using the user-written xblc command by Nicola Orsini. I'm using a new dataset, and this time my code doesn't produce the graph I'm used to. Here's the dataset, the code and the resulting graph. Can anyone spot the error?

BLF_fall_kontroll: 0=controls, 1=cases
enddate_bmi: end of follow-up
deceased....: date of death
BLF_unddat: date of origin
BMI: BMI
BLF_sex: 0=women, 1=men

* Example generated by -dataex-. To install: ssc install dataex
clear
input float id double BLF_fall_kontroll float enddate_bmi double(deceased_20160419 BLF_unddat BMI BLF_sex)
  1 1 20020902 1 19970303  25.50361570247934 1
  2 1    20763 0 19970311  22.77318640955005 0
  3 1 20140408 1 19970311  25.55932915514163 1
  4 1    20763 0 19970319 29.860551225775623 1
  5 1    20763 0 19970414 20.957171162932475 0
  6 1 20021230 1 19970417 38.805697589481376 0
  7 1    20763 0 19970418 24.933720489837143 1
  8 1    20763 0 19970421  21.71806608974573 1
  9 1 20101012 1 19970421 22.481329065691202 0
 10 1 20130410 1 19970421  19.77769866698311 0
 11 1 20090528 1 19970429  26.91272587466359 0
 12 1 20160224 1 19970502   25.5649539199596 1
 13 1    20763 0 19970506 29.860551225775623 1
 14 1 20140512 1 19970506  37.34186861758877 0
 15 1    20763 0 19970513  26.89232313815483 0
 16 1    20763 0 19970515  26.59279778393352 1
 17 1    20763 0 19970528  23.38868655818771 1
 18 1    20763 0 19980511 26.149276859504134 1
 19 1    20763 0 19980511 25.082863029651524 1
 20 1    20763 0 19980511 16.298185941043087 0
 21 1 20030924 1 19980511 23.147255121330193 0
 22 1 20120224 1 19980513 28.293345405160707 1
 23 1    20763 0 19980603 27.993022029291247 0
 24 1 20110612 1 19980603 25.390624999999996 0
 25 1    20763 0 19980604 23.671253629592222 1
 26 1 20120104 1 19980604 25.510204081632658 1
 27 1 20101120 1 19980610 29.054752066115704 1
 28 1    20763 0 19990923 20.549886621315196 0
 29 1    20763 0 19991012 29.012345679012345 1
 30 1    20763 0 19991012 25.781249999999996 1
 31 1    20763 0 19991102 23.661438615467823 0
 32 1    20763 0 19991108 20.281233098972418 0
 33 1    20763 0 19991110 23.735308416025617 1
 34 1    20763 0 19991112 26.775934114974238 0
 35 1    20763 0 19991112 28.060018903591683 1
 36 1    20763 0 19991123 24.221453287197235 0
 37 1 20080208 1 19991209 20.904195011337873 0
 38 1    20763 0 20000103 29.396221429515126 1
 39 1    20763 0 20000124 30.863035868869737 1
 40 1    20763 0 20000204  31.58861340679523 0
 41 1 20031012 1 20000309  26.42356982428326 1
 42 1 20050812 1 20000413  33.13975508142911 1
 43 1    20763 0 20000530 19.227687870533565 0
 44 1    20763 0 20000620 27.471707127713575 1
 45 1 20111232 1 20000628 26.874496103198062 1
 46 1    20763 0 20000629  23.56663223140496 1
 47 1    20763 0 20010314 26.023048986244955 1
 48 1    20763 0 20010403  26.82742078020452 1
 49 1    20763 0 20010403 22.058051188683873 0
 50 1    20763 0 20010405 28.554631729234906 1
 51 1    20763 0 20010417 26.769779892920884 0
 52 1    20763 0 20010419 20.077334919690664 0
 53 1 20150228 1 20010419  21.79944510503369 1
 54 1    20763 0 20010504  22.86236854138088 0
 55 1    20763 0 20010508  22.34029706557179 1
 56 1    20763 0 20010516  25.33500198406642 1
 57 1    20763 0 20011024  28.73174689021093 0
 58 1    20763 0 20011025  26.82742078020452 0
 59 1    20763 0 20011031 26.672763298277697 0
 60 1    20763 0 20011107 18.670934308794386 0
 61 1    20763 0 20011113   25.4364666435426 1
 62 1    20763 0 20011119 29.935443565181178 1
 63 1    20763 0 20011213  22.95908765854944 0
 64 1    20763 0 20020205 21.192742415229034 0
 65 1    20763 0 20020206 21.296296296296294 1
 66 1    20763 0 20020210 28.081632653061224 1
 67 1    20763 0 20020305 23.661438615467823 0
 68 1    20763 0 20020305 25.529644871208653 0
 69 1    20763 0 20020306 22.052190183434128 1
 70 1    20763 0 20020312 25.351541373715524 0
 71 1    20763 0 20020313 26.014568158168572 1
 72 1    20763 0 20020313  32.14024835646457 1
 73 1    20763 0 20020527  23.66691015339664 1
 74 1    20763 0 20020902  27.44059917355372 1
 75 1    20763 0 20020902 38.505239237470015 1
 76 1    20763 0 20020902  35.57941387597141 1
 77 1    20763 0 20020902 24.307243558580453 1
 78 1    20763 0 20020905  24.56747404844291 0
 79 1    20763 0 20020905  30.86300682844026 0
 80 1    20763 0 20020909 26.314635323012148 0
 81 1    20763 0 20020909  25.21735857578381 0
 82 1 20131014 1 20020909  25.10387811634349 0
 83 1 20140408 1 20020909 24.111507464658473 1
 84 1    20763 0 20020910 20.904195011337873 0
 85 1    20763 0 20020910 24.755464315903875 1
 86 1 20041112 1 20020910  20.04744562130375 0
 87 1 20110122 1 20020910 22.944088878154812 1
 88 1    20763 0 20020911   24.3046178773967 0
 89 1 20050224 1 20020911  24.76756591982929 0
 90 1 20051108 1 20020911 23.671253629592222 1
 91 1 20070512 1 20020911 30.449826989619382 1
 92 1    20763 0 20020912  27.74474831549742 1
 93 1    20763 0 20020912 25.180785123966942 1
 94 1 20070908 1 20020912 25.727555214006482 1
 95 1 20150500 1 20020913  26.26494384736143 1
 96 1    20763 0 20020916  24.76756591982929 0
 97 1    20763 0 20020916 21.333333333333332 0
 98 1 20140716 1 20020916 23.889462809917354 1
 99 1    20763 0 20020917  24.96494647925858 1
100 1    20763 0 20020918 27.717685235262305 1
end
format %td enddate_bmi
label values BLF_fall_kontroll BLF_fall_kontroll
label def BLF_fall_kontroll 1 "Fall (FEV1/(max av FVC och EVC)<0.7 pre-BD)", modify
label values deceased_20160419 deceased_20160419
label def deceased_20160419 0 "Not deceased", modify
label def deceased_20160419 1 "Deceased", modify
label values BLF_sex BLF_sex
label def BLF_sex 0 "Kvinna", modify
label def BLF_sex 1 "Man", modify

gen id = _n

replace BMI=round(BMI,.5)
tabstat BMI, by(BLF_fall_kontroll) stat(n mean median min max p1 p99)

gen enddate_bmi = mdy(11,05,2016)
format enddate_bmi %td
label variable enddate_bmi "End of follow-up date"
replace enddate_bmi = BLF_avlidendat_ratt if (deceased_20160419==1)

browse BMI BLF_unddat enddate_bmi BLF_fall_kontroll in 1/100

foreach num of numlist 3/7{
        preserve
        keep if BLF_fall_kontroll==0        
        stset enddate_bmi, id(id) failure(deceased_20160419==1) origin(time BLF_unddat) scale(365.25)
        mkspline spl_bmi = BMI, cubic nknots(`num') displayknots            
        stcox c.spl_bmi* i.BLF_sex, vce(robust)
        estat ic
        levelsof BMI, local(levels)
        xblc spl_bmi*, covname(BMI) at(`levels') reference(26.3) eform gen(vbmi hr lb ub)
        keep if vbmi>16.0 & vbmi<48.5
        twoway rline lb ub vbmi, lp(solid) lc(red) lw(medium) || line hr vbmi, lc(blue) lp(solid) lw(medium) ///
        legend(off) ylabel(, nogrid format(%3.2f)) yticks() xlabel(16(1)48, format(%3.0f)) xticks() xtitle("{bf:BMI(kg/m{sup:2})}") ytitle("{bf:HR (95% CI) for all-cause mortality}") ///
        yline(1, lc(black) lp(dash) lw(medthin)) name(no_copd_death_spl_bmi_knot`num', replace) saving("C:\.gph",replace)
        restore
}