Windows 7
I am running normalmixEM to fit two normal curves to my data. For some reason,
that I don't understand, the results of running the function twice, on the same
data, results in two different (although similar) sets of values. I would
expect the function run twice on the same data would give exactly the same
results!
I ran the program below and got the following results:
lambda1 mu1 lambda1 lambda2 lambda2 mu2
0.5030387 31.5172824 0.5030387 0.4969613 0.4969613 104.9249404
> run2
lambda1 mu1 lambda1 lambda2 lambda2 mu2
0.5030406 31.5174149 0.5030406 0.4969594 0.4969594 104.9251556
#Define data
John<-c(9.181 ,9.464 ,9.464 ,10.265 ,11.477 ,11.477 ,11.477 ,12.361,
12.361 ,12.361 ,12.361 ,12.985 ,12.985 ,13.384 ,13.384 ,13.962,
14.517 ,14.698 ,14.698 ,14.698 ,14.698 ,15.398 ,15.398 ,16.231,
16.231 ,16.552 ,16.552 ,16.711 ,16.711 ,17.481 ,17.481 ,17.481,
17.927 ,18.506 ,18.506 ,18.928 ,18.928 ,18.928 ,19.612 ,19.612,
19.745 ,19.745 ,20.530 ,20.530 ,21.162 ,21.162 ,21.162 ,21.162,
21.162 ,21.776 ,21.776 ,22.607 ,22.607 ,22.723 ,22.954 ,23.408,
23.632 ,25.353 ,25.353 ,25.663 ,25.663 ,25.663 ,25.969 ,26.171,
26.171 ,26.171 ,26.768 ,27.544 ,27.640 ,27.640 ,27.735 ,28.761,
29.215 ,29.840 ,30.190 ,30.881 ,30.881 ,31.220 ,31.220 ,31.220,
31.888 ,31.888 ,32.135 ,32.461 ,32.461 ,32.623 ,33.104 ,34.123,
35.855 ,35.928 ,35.928 ,36.293 ,36.293 ,37.012 ,37.366 ,37.366,
37.366 ,37.647 ,37.850 ,37.856 ,37.856 ,38.202 ,38.202 ,38.954,
39.021 ,39.089 ,39.089 ,39.223 ,39.491 ,39.624 ,40.153 ,40.609,
40.868 ,41.380 ,41.380 ,42.200 ,42.324 ,42.324 ,42.324 ,43.126,
43.853 ,43.853 ,44.152 ,44.568 ,45.213 ,45.446 ,45.562 ,46.193,
46.193 ,46.421 ,47.320 ,48.203 ,48.257 ,49.284 ,49.656 ,50.550,
50.550 ,51.938 ,52.342 ,52.342 ,52.342 ,52.393 ,53.586 ,53.733,
54.560 ,55.184 ,55.280 ,56.691 ,57.384 ,57.384 ,57.522 ,59.856,
59.856 ,60.599 ,61.975 ,65.004 ,68.861 ,69.052 ,69.811 ,70.897,
71.267 ,71.489 ,73.056 ,74.485 ,74.732 ,75.189 ,76.439 ,77.126,
77.670 ,77.975 ,78.514 ,80.338 ,80.600 ,83.173 ,83.205 ,83.553,
84.181 ,84.960 ,86.160 ,86.405 ,86.618 ,87.646 ,89.284 ,89.401,
89.989 ,90.456 ,90.892 ,90.892 ,90.950 ,91.412 ,91.729 ,92.072,
92.273 ,92.330 ,92.529 ,92.870 ,93.661 ,94.194 ,94.640 ,94.807,
95.029 ,95.112 ,95.885 ,96.132 ,96.869 ,97.438 ,97.600 ,98.567,
99.020 ,99.020 ,99.127 ,100.683 ,100.683 ,101.231 ,102.266 ,102.498,
102.883 ,103.113 ,103.291 ,103.800 ,103.927 ,104.332 ,104.685 ,104.685,
104.710 ,105.911 ,106.333 ,107.073 ,107.123 ,107.172 ,107.172 ,107.907,
107.907 ,108.272 ,108.272 ,108.345 ,108.564 ,108.758 ,109.338 ,110.201,
110.201 ,110.559 ,111.130 ,111.438 ,111.556 ,112.004 ,112.004 ,112.004,
112.684 ,112.940 ,112.940 ,113.034 ,113.661 ,113.661 ,113.962 ,113.985,
114.031 ,114.607 ,114.607 ,114.768 ,115.249 ,115.797 ,116.069 ,116.160,
117.041 ,117.154 ,117.983 ,118.473 ,118.473 ,118.495 ,118.495 ,118.762,
119.027 ,120.501 ,120.959 ,122.000 ,122.022 ,123.396 ,123.609 ,123.737,
124.035 ,124.416 ,124.818 ,124.881 ,124.881 ,125.071 ,125.387 ,125.576,
127.636 ,128.089 ,128.233 ,132.675 ,133.566 ,134.509 ,134.666 ,135.037,
135.504 ,136.589 ,138.675 ,141.961 ,144.608 ,155.222 ,158.646 ,168.502)
# First run of normalmixEM
mixmdl = normalmixEM(John)
run1<-c(lambda1=mixmdl$lambda[1],mu1=mixmdl$mu[1],lambda=mixmdl$lambda,lambda2=mixmdl$lambda[2],mu2=mixmdl$mu[2])
#Second run of normalmixEM
mixmdl = normalmixEM(John)
# Results are not the same!
run2<-c(lambda1=mixmdl$lambda[1],mu1=mixmdl$mu[1],lambda=mixmdl$lambda,lambda2=mixmdl$lambda[2],mu2=mixmdl$mu[2])
run1
run2
John David Sorkin M.D., Ph.D.
Professor of Medicine
Chief, Biostatistics and Informatics
University of Maryland School of Medicine Division of Gerontology and Geriatric
Medicine
Baltimore VA Medical Center
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524
(Phone) 410-605-7119
(Fax) 410-605-7913 (Please call phone number above prior to faxing)
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