约束nlsLM（）与R中

Question

成本函数我有一个数据帧df

df<- structure(list(ID = structure(c(1L, 3L, 5L, 11L, 12L, 13L, 14L, 
15L, 16L, 17L, 18L, 19L, 20L, 21L, 22L, 23L, 24L, 25L, 26L, 27L, 
31L, 32L, 33L, 36L, 37L, 40L, 41L, 44L, 45L, 46L, 47L, 48L, 49L, 
50L, 52L, 53L, 54L, 56L, 57L, 58L, 60L, 62L, 63L, 66L, 67L, 68L, 
69L, 70L, 71L, 72L, 75L, 77L, 80L, 81L, 82L, 88L, 93L, 95L, 97L, 
99L, 101L, 102L, 107L, 108L, 114L), .Label = c("AU-Tum", "AU-Wac", 
"BE-Bra", "BE-Jal", "BE-Vie", "BR-Cax", "BR-Ma2", "BR-Sa1", "BR-Sa3", 
"BW-Ma1", "CA-Ca1", "CA-Ca2", "CA-Ca3", "CA-Gro", "Ca-Man", "CA-NS1", 
"CA-NS2", "CA-NS3", "CA-NS4", "CA-NS5", "CA-NS6", "CA-NS7", "CA-Oas", 
"CA-Obs", "CA-Ojp", "CA-Qcu", "CA-Qfo", "CA-SF1", "CA-SF2", "CA-SF3", 
"CA-SJ1", "CA-SJ2", "CA-SJ3", "CA-TP1", "CA-TP2", "CA-TP4", "CN-Cha", 
"CN-Ku1", "CZ-Bk1", "De-Bay", "DE-Hai", "DE-Har", "DE-Meh", "DE-Tha", 
"DE-Wet", "DK-Sor", "ES-Es1", "FI-Hyy", "FI-Sod", "FR-Fon", "FR-Hes", 
"FR-Lbr", "FR-Pue", "GF-Guy", "ID-Pag", "IL-Yat", "IT-Col", "IT-Cpz", 
"IT-Lav", "IT-Lma", "IT-Noe", "IT-Non", "IT-Pt1", "IT-Ro1", "IT-Ro2", 
"IT-Sro", "JP-Tak", "JP-Tef", "JP-Tom", "NL-Loo", "PT-Esp", "RU-Fyo", 
"RU-Zot", "SE-Abi", "SE-Fla", "SE-Nor", "SE-Sk1", "SE-Sk2", "SE-St1", 
"UK-Gri", "UK-Ham", "US-Bar", "US-Blo", "US-Bn1", "US-Bn2", "Us-Bn3", 
"US-Dk2", "US-Dk3", "US-Fmf", "US-Fwf", "US-Ha1", "US-Ha2", "US-Ho1", 
"US-Ho2", "US-Lph", "US-Me1", "US-Me3", "US-Nc2", "US-NR1", "US-Oho", 
"US-So2", "US-So3", "US-Sp1", "US-Sp2", "US-Sp3", "US-Syv", "US-Umb", 
"US-Wbw", "US-Wcr", "US-Wi0", "US-Wi1", "US-Wi2", "US-Wi4", "US-Wi8", 
"VU-Coc", "CA-Cbo", "CN-Lao", "ID-Buk", "IS-Gun", "JP-Fuj", "MY-Pso", 
"RU-Ab", "RU-Be", "RU-Mix", "TH-Mae"), class = "factor"), Y = c(436.783385497984, 
55.1825021383702, 526.4133417369, 391.49284084118, -519.814235572849, 
11.5525291214872, 162.441016515717, 39.0395567645998, -70.4910326673707, 
17.1155716306239, -106.326129257097, -94.9308303585276, -66.4285516217351, 
-144.929052323413, -220.613145695315, 157.129576861289, 44.1257786633602, 
46.8326830295943, -146.719591499443, 30.8043649939355, -4.10548956954153, 
-108.258462657337, 90.3369144331664, 126.866108251153, 42.9489971246803, 
-45.4886732113082, 483.932040393885, 590.754048774834, 82.1480000555981, 
76.8863707484328, 404.007940533033, 202.629066249886, -46.9675149230141, 
557.939170770813, 300.979565786038, 224.256197650044, 148.719307398695, 
201.195892312115, 466.727302447427, 552.762670615377, 595.145436977735, 
481.359543363331, 467.379381521489, 444.812610935212, 308.198167469197, 
-638.973101716489, 321.395064735785, 181.896345832773, 629.214319321327, 
-176.181996958815, 59.1716887350485, -186.42650026083, 515.533437888983, 
595.091753601562, 367.15020653978, 934.415348643437, 255.499246957091, 
368.347069109092, 141.97570288631, 39.5917358684237, 105.039591642989, 
77.9087587283187, 153.700042322307, 157.436949779134, 358.242634316906 
), Unc = c(-2.87896446519996, -0.30731156873436, -1.3811336535939, 
-3.60168125065523, 1.35359565655672, -0.58525692609091, -0.463995294634932, 
-0.112770209421705, -0.178508318809592, -0.44506337354913, 0.285085608169751, 
0.241425707960461, -0.616179720920167, -0.00579570274186878, 
0.385699289486463, -0.43071884834486, -1.32799753416588, -0.1382487377, 
0.026437443324628, -0.0981101016865843, -0.125326368431498, 0.289668409902704, 
-0.224679559714174, -0.376257445433255, -0.0904535633017475, 
-1.27942478849042, -2.78944896222686, -1.57015451106923, -3.02435991211342, 
-0.188885650489005, -2.77697810019308, -0.683634153351544, 0.148164853468482, 
-1.520102142822, -0.855422614115418, -0.580609573477037, -2.12306082165876, 
-1.2334420909422, -2.00323122411995, -1.45967340674881, -1.60448511158608, 
-2.52530298868671, -1.28908559855364, -1.16270411420386, -1.5186009244046, 
0.24330408272554, -1.72852090322909, -0.497423296440042, -2.79905035399537, 
0.453520174531953, -0.38557736709315, 0.513504024431323, -1.58608831551316, 
-1.56046815861851, -3.32259575879769, -7.99135003959363, -0.913109035398266, 
-3.48447862397436, -0.518022500487711, -0.352263975401941, -0.331662926968978, 
-0.236234610041281, -2.31039763656225, -0.987148209221828, -3.37441047823435 
), X = c(98.5, 77, 63.2222222222222, 52.5, 3.5, 15.5, 71, 161.833333333333, 
153.5, 73, 39, 40, 23, 14, 5.5, 78, 129.5, 73.5, 4, 100, 10, 
3, 30, 65.5, 198, 45.5, 20, 111.5, 44, 68.5, 102.5, 39.1111111111111, 
83.8, 136, 31.5, 56.5, 101, 39.25, 108.5, 52.1666666666667, 54.5, 
9.5, 13, 52.1428571428571, 66.5, 1, 44.25, 106, 19, 202.571428571429, 
36.6, 2, 21.2, 69, 67.5, 21, 135, 46.5, 17.5, 96, 80.6666666666667, 
10.6666666666667, 86.5, 66.2, 2.5)), .Names = c("ID", "Y", "Unc", 
"X"), row.names = c(1L, 2L, 3L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 
12L, 13L, 14L, 15L, 16L, 17L, 18L, 19L, 20L, 21L, 22L, 23L, 24L, 
25L, 26L, 27L, 28L, 29L, 30L, 31L, 32L, 33L, 34L, 35L, 36L, 37L, 
38L, 39L, 40L, 41L, 42L, 43L, 44L, 45L, 46L, 47L, 48L, 49L, 50L, 
51L, 53L, 54L, 55L, 56L, 57L, 58L, 59L, 60L, 61L, 62L, 63L, 64L, 
65L, 66L, 67L), class = "data.frame", na.action = structure(c(4L, 
52L, 68L, 69L, 70L, 71L, 72L, 73L, 74L, 75L, 76L, 77L), .Names = c("4", 
"52", "68", "69", "70", "71", "72", "73", "74", "75", "76", "77" 
), class = "omit")) 

我目前正在与一个离开一个执行非线性回归分析出ID如下：

library (minpack.lm) 
id<-unique(df$ID) 
nlm1_pred<- c() 
for (i in id){ 
    nlm1<- try(nlsLM(Y~offset + A*(1-exp(k*X)), data = df[df$ID != i,], 
         start = list(A=192.93829, k=-0.08976, offset=-700), control = list(maxiter = 500)), silent=TRUE); 
    nlm1_pred[[i]]<- if (inherits(nlm1, "nls")) sim = predict(nlm1, newdata=df[df$ID == i,]) else NA; 
} 

基本上，对于每次迭代，我删除一个ID并使用其他ID来执行非线性回归模型，然后用它来预测剩余ID的响应。

但是，用于创建非线性模型的每个观测值具有不同的不确定性值（请参见df中的Unc列）。因此，我想根据我的观察结果的不确定性在nls中包含一个成本函数。我做了一些研究，下面的成本函数应该做的工作：cost= sum(((obs-pred)/ Unc)^2)这基本上是由不确定性加权的平方误差（SEE）的总和。

我遇到了麻烦，找到一种方法将这个成本函数包含在nlsLM()对象中。我已经看到weights参数可以包含在nlsLM()对象中，但该参数的可能性看起来相当有限。

这是我通过在nlsLM（）函数的权重参数，到目前为止已经试过，但它不工作至今：

id<-unique(df$ID) 
    nlm1_pred<- c() 
    for (i in id){ 
     nlm1<- try(nlsLM(Y~offset + A*(1-exp(k*X)), data = df[df$ID != i,], 
          start = list(A=192.93829, k=-0.08976, offset=-700), control = list(maxiter = 500), weights = wfct(sum(((fitted-Y)/Unc)^2))), silent=TRUE); 
     nlm1_pred[[i]]<- if (inherits(nlm1, "nls")) sim = predict(nlm1, newdata=df[df$ID == i,]) else NA; 
    } 

任何人都可以帮助我在这？

Answer 1

您可以使用1/Unc^2作为权重nlsLM获得被称为在问题cost和obj.w下面的目标函数。

为了说明，使用optim和nlsLM两个非加权的例子下面给出相同的结果和两个加权的例子（也使用optim和nlsLM）给出相同的结果。由于这里的目标是要表明权重是相同的，我们在每种情况下都使用与最终值非常接近的起始值，这样算法中的差异就不会发挥作用。

rhs <- function(p, df) with(df, p[[3]] + p[[1]]*(1-exp(p[[2]]*X))) 

# unweighted 

st.u <- list(A = 800, k = -0.2, offset = -700) 
obj.u <- function(p, df) with(df, sum((Y - rhs(p, df))^2)) 

fit.optim.u <- optim(st.u, obj.u, df = df) 
fit.optim.u$par; fit.optim.u$value # 1 

fit.nlsLM.u <- nlsLM(Y ~ rhs(c(A, k, offset), df), data = df, start = st.u) 
coef(fit.nlsLM.u); deviance(fit.nlsLM.u) # 2 - same as 1 

# weighted 

st.w <- list(A = 2704, k = -1.7, offset = -2845) 
obj.w <- function(p, df) with(df, sum((Y - rhs(p, df))^2/Unc^2)) 

fit.optim.w <- optim(st.w, obj.w, df = df) 
fit.optim.w$par; fit.optim.w$value # 3 

fit.nlsLM.w <- nlsLM(Y ~ rhs(c(A, k, offset), df), data = df, weights = 1/Unc^2, 
    start = st.w) 
coef(fit.nlsLM.w); deviance(fit.nlsLM.w) # 4 = same as 3 

看来，正是你想要的目标函数/权重仍然不清楚，所以你可能想用实例来发挥上述使用optim，直到你找到你想要的目标函数（因为它的目标是明确的），然后在nlsLM中执行它，检查它们是否给出相同的答案。请注意，即使由于不同的算法和停止标准而使用相同的目标/权重，optim和nlsLM也可以找到不同的答案，因此，如果您同时运行并发现然后尝试以最佳系数开始消除差异。

所有这一切的一点是，由于optim我们明确指定的目标，而不是nlsLM它提供了双重检查什么nlsLM正在做什么的方式。

更新：重新集中比较优化和nlsLM。