{smcl} {* 13jan2017} {* 13jun2017}{...} {cmd:help albatross_examples} {hline} {title:Albatross Examples} {phang} {bf:albatross examples} {hline 2} The code used to simulate {cmd: albatross} examples (see {help albatross}) {title:Mean} {p 4 4 2} Basic albatross plot . {stata clear} . {stata set obs 20} . {stata set seed 100} . {stata gen n = 10+490*runiform()} . {stata gen mean_dif = 0.2*runiform()} . {stata gen sd = 1+4*runiform()} . {stata gen se = sd/sqrt(n)} . {stata gen p = 2*normal(-abs(mean_dif/se))} . {stata albatross n p mean_dif, type(mean) sd(sd)} {p 4 4 2} Use the standard deviation to adjust to the effective sample size . {stata albatross n p mean_dif, type(mean) sd(sd) adjust} {title:Proportion} {p 4 4 2} Basic albatross plot . {stata clear} . {stata set obs 20} . {stata set seed 100} . {stata gen n = 10+490*runiform()} . {stata gen prop_dif = 0.1+0.1*runiform()} . {stata gen se = sqrt(prop_dif*(1-prop_dif)/n)} . {stata gen p = 2*normal(-abs(prop_dif/se))} . {stata albatross n p prop_dif, type(proportion)} {p 4 4 2} Plot specifying the proportion to be 0.15 in all contours . {stata albatross n p prop_dif, type(proportion) spro(0.15)} {title:Correlation coefficient} – equivalently, {title:beta} {p 4 4 2} Basic albatross plot . {stata clear} . {stata set obs 20} . {stata set seed 100} . {stata gen n = 10+490*runiform()} . {stata gen corr = 0.2*runiform()} . {stata gen se = sqrt((1-corr^2)/n)} . {stata gen p = 2*normal(-abs(corr/se))} . {stata gen by = "Large"} . {stata replace by = "Small" if corr<0.1} . {stata albatross n p corr, type(correlation)} {p 4 4 2} Plot split by “large” and “small” in color . {stata albatross n p corr, type(correlation) by(by) color} {title:Mean difference} {p 4 4 2} Basic albatross plot, assuming only the mean difference and standard deviation are known . {stata clear} . {stata set obs 20} . {stata set seed 100} . {stata gen n = 10+490*runiform()} . {stata gen sd1 = 0.5+0.5*runiform()} . {stata gen sd2 = 0.5+0.5*runiform()} . {stata gen r = 1+3*runiform()} . {stata gen n1 = r*n/(1+r)} . {stata gen n2 = n/(1+r)} . {stata gen sd = sqrt((sd1^2*n1+sd2^2*n2)/n)} . {stata gen md = 0.1+0.1*rnormal()} . {stata gen se = sqrt(sd1^2/n1 + sd2^2/n2)} . {stata gen p = 2*normal(-abs(md/se))} . {stata albatross n p md, type(md) sd(sd)} {p 4 4 2} Use the standard deviation of both groups and proportion of cases to controls to estimate the effective sample sizes . {stata albatross n p md, type(md) sd1(sd1) sd2(sd2) r(r) adjust} {p 4 4 2} Define the contours better . {stata albatross n p md, type(md) sd1(sd1) sd2(sd2) r(r) adjust contours(0.2 0.4 0.6)} {title:Standardised mean difference} {p 4 4 2} Basic albatross plot . {stata clear} . {stata set obs 20} . {stata set seed 100} . {stata gen n = 10+490*runiform()} . {stata gen smd = -0.5+0.25*runiform()} . {stata gen r = 1+3*runiform()} . {stata gen se = sqrt((2*(r+1)^2+r*smd^2)/(2*r*n))} . {stata gen p = 2*normal(-abs(smd/se))} . {stata gen range = 1 if p >0.1} . {stata replace p = 0.1 if p > 0.1} . {stata albatross n p smd, type(smd)} {p 4 4 2} Plot with range specified, so lines are produced for studies with P > 0.1 . {stata albatross n p smd, type(smd) range(range)} {p 4 4 2} Plot with titles, range, two contours specified . {stata albatross n p smd, type(smd) contours(0.25 0.5) range(range) title("When P values are inexact, data simulated", size(medium))} {p 4 4 2} Plot with titles, range and restricted to n > 250 in the first 10 studies . {stata albatross n p smd if n > 250 in 1/10, type(smd) contours(0.25 0.5 1) range(range) title("When P values are inexact (restricted), data simulated", size(small))} {p 4 4 2} No plot, but display Fisher's and Stouffer's combined P values . {stata albatross n p smd, type(smd) nograph fishers stouffers} {title:Relative risks and odds ratios} {p 4 4 2} Basic albatross plot . {stata clear} . {stata set obs 20} . {stata set seed 100} . {stata gen a = 300+200*runiform()} . {stata gen b = a*1.5} . {stata gen c = 300+200*runiform()} . {stata gen d = 300+200*runiform()} . {stata gen n = a+b+c+d} . {stata gen rr = a*(c+d)/(c*(a+b))} . {stata gen or = a*d/(b*c)} . {stata gen n1 = a+b} . {stata gen n2 = c+d} . {stata gen baseline = c/(c+d)} . {stata gen r = n1/n2} . {stata gen se_rr = sqrt(1/a+1/c-1/n1-1/n2)} . {stata gen se_or = sqrt(1/a+1/b+1/c+1/d)} . {stata gen p_rr = 2*normal(-abs(ln(rr)/se_rr))} . {stata gen p_or = 2*normal(-abs(ln(or)/se_or))} . {stata replace p_or = 10^-30 if p_or == 0} . {stata gen e = 1 if ln(rr) >= 0} . {stata replace e = -1 if e == .} . {stata gen by = 1 if a > 400} . {stata replace by = 0 if a <= 400} . {stata albatross n p_rr e, type(rr) baseline(baseline)} . {stata albatross n p_or e, type(or) baseline(baseline)} {p 4 4 2} Fully specified plot with estimated effective sample size . {stata albatross n p_rr e, type(rr) baseline(baseline) r(r) adjust} . {stata albatross n p_or e, type(or) baseline(baseline) r(r) adjust} {p 4 4 2} Fully specified plot with estimated effective sample size, with standardised r and baseline specified, split into two variables and in color . {stata albatross n p_rr e, type(rr) baseline(baseline) r(r) adjust sr(2) sbaseline(0.5) by(by) color} . {stata albatross n p_or e, type(or) baseline(baseline) r(r) adjust sr(2) sbaseline(0.5) by(by) color} {title:Authors} {p 4 4 2} Sean Harrison ({browse "mailto:sean.harrison@bristol.ac.uk":sean.harrison@bristol.ac.uk}). School of Social and Community Medicine, University of Bristol, Canynge Hall, Whiteladies Road, Bristol BS8 2PS, UK {title:References} {p 4 4 2} Harrison, S., Jones, H.E., Martin, R.M., Lewis, S., Higgins, J.P.T. The albatross plot: a novel graphical tool for presenting results of diversely reported studies in a systematic review. {it:Harrison S, Jones HE, Martin RM, Lewis SJ, Higgins JP. The albatross plot: a novel graphical tool for presenting results of diversely reported studies in a systematic review. Res Synth Methods. 2017}. {p 4 4 2} Harrison, S., Jones, H.E., Martin, R.M., Lewis, S., Higgins, J.P.T. 2017. The albatross plot program: a novel graphical tool for presenting results of diversely reported studies in a systematic review in Stata. {it:Currently Unpublished}.