线性混合自然样条模型在峰值速度下的个体年龄 [英] Individual age at peak velocity from linear mixed natural spline model

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本文介绍了线性混合自然样条模型在峰值速度下的个体年龄的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!

问题描述

该线程继续从线性混合样条模型中获取特定于受试者的峰值速度和年龄,以峰值速度值./p>


我正在为具有年龄的自然样条函数的线性混合效果模型拟合.我想通过区分样条曲线项来估计数据集中每个人的峰值速度(apv-年)和峰值速度(pv-克)的年龄.该模型包括一个随机的年龄二次方斜率.

我如何估算个人特定的apv和pv?我正在使用 SplinesUtils 包.

示例数据:

  dat<-结构(list(id = c(1001L,1001L,1001L,1001L,1001L,1002L,1003L,1004L,1004L,1004L,1004L,1004L,1004L,1004L,1005L,1005L,1005L,1005L,1005L,1006L,1006L,1006L,1006L,1006L,1007L,1007L,1008L,1008L,1008L,1008L,1008L,1009L,1009L,1009L,1010L,1010L,1010L,1011L,1012L,1012L,1012L,1013L,1013L,1014L,1015L,1015L,1015L,1016L,1016L,1016L,1016L,1016L,1017L,1017L,1018L,1020L,1020L,1021L,1021L,1021L,1021L,1022L,1022L,1023L,1023L,1023L,1023L,1023L,1023L,1023L,1023L,1023L,1023L,1024L,1024L,1024L,1024L,1024L,1025L,1025L,1025L,1026L,1026L,1026L,1026L,1027L,1027L,1028L,1028L,1028L,1028L,1028L,1028L,1028L,1029L,1029L,1029L,1029L,1029L,1029L,1030L,1030L,1030L,1030L,1030L,1030L,1030L,1030L,1031L,1031L,1031L,1031L,1032L,1032L,1032L,1032L,1032L,1033L,1033L,1033L,1033L,1034L,1034L,1034L,1034L,1034L,1035L,1035L,1036L,1037L,1037L,1037L,1037L,1039L,1039L,1040L,1040L,1040L,1040L,1040L,1040L,1041L,1041L,1041L,1041L,1041L,1041L,1042L,1042L,1042L,1042L,1042L,1042L,1042L,1043L,1043L,1043L,1043L,1044L,1044L,1044L,1045L,1045L,1045L,1045L,1045L,1045L,1047L,1048L,1048L,1049L,1049L,1049L,1049L,1051L,1051L,1052L,1052L,1052L,1052L,1052L,1053L,1053L,1053L,1053L,1053L,1054L,1054L,1054L,1054L,1054L,1054L,1054L,1054L,1056L,1056L,1056L,1056L,1057L,1057L,1058L,1058L,1058L,1058L,1058L,1060L,1060L,1060L,1061L,1061L,1061L,1061L,1061L,1062L,1062L,1062L,1062L,1062L,1063L,1063L,1063L,1064L,1064L,1064L,1064L,1065L,1065L,1066L,1066L,1066L,1066L,1066L,1066L,1067L,1067L,1067L,1068L,1068L,1068L,1068L,1068L,1068L,1068L,1069L,1070L,1070L,1070L,1071L,1071L,1071L,1072L,1072L,1072L,1072L,1072L,1073L,1073L,1073L,1073L,1074L,1074L,1074L,1075L,1075L,1075L,1075L,1075L,1075L,1076L,1076L,1076L,1077L,1077L,1077L,1077L,1077L,1077L,1078L,1078L,1078L,1078L,1078L,1078L,1078L,1080L,1080L,1080L,1080L,1081L,1081L,1082L,1082L,1082L,1083L,1083L,1084L,1085L,1085L,1085L,1085L,1085L,1085L,1086L,1086L,1086L,1087L,1087L,1087L,1087L,1087L,1087L,1087L,1087L,1088L,1088L,1088L,1088L,1089L,1089L,1089L,1089L,1089L,1090L,1090L,1091L,1091L,1091L,1091L,1091L,1092L,1092L,1092L,1092L,1092L,1093L,1093L,1093L,1093L,1094L,1094L,1094L,1094L,1094L,1095L,1095L,1095L,1095L,1096L,1097L,1097L,1098L,1098L,1098L,1098L,1098L,1099L,1099L,1099L,1099L,1099L,1099L,1099L,1099L,1100L,1100L,1100L,1101L,1101L,1101L,1101L,1103L,1103L,1103L,1103L,1103L,1103L,1103L,1104L,1104L,1104L,1104L,1105L,1105L,1105L,1106L,1106L,1106L,1106L,1106L,1106L,1106L,1106L,1106L,1107L,1108L,1110L,1111L,1112L,1117L,1123L),y = 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

拟合线性混合样条线模型的代码:

 库(nlme)库(样条)图书馆(tidyverse)nspline_model<-lme(y〜ns(age,df = 3),data = dat,random =〜poly(age,2)| id) 

这是显示我如何尝试计算两个人的apv和pv的代码-但是我得到的pv值为负,apv值为〜39年

 #个人ID列表dat%>%distinct(id)%>%pull()图书馆(SplinesUtils)(random_quadratic<-random.effects(nspline_model))spl_population_unshifted<-RegSplineAsPiecePoly(nspline_model,"ns(age,df = 3)",FALSE)#ID = 1001(coef_1001<-spl_population_unshifted $ PiecePoly $ coef)coef_1001 [1,]<-coef_1001 [1,] + random_quadratic [1,1]coef_1001 [2,]<-coef_1001 [2,] + random_quadratic [1,2] + random_quadratic [1,3]spl_1001_unshifted<-spl_population_unshiftedspl_1001_unshifted $ PiecePoly $ coef<-coef_1001(apv_1001<-求解(spl_1001_unshifted,b = 0,导数= 2))(pv_1001<-预测(spl_1001_unshifted,apv_1001,导数= 1))(apv_pv_1001<-as.data.frame(cbind(apv_1001,pv_1001)))(apv_pv_1001<-apv_pv_1001%&%;%top_n(1,pv_1001))#ID = 1002(coef_1002<-spl_population_unshifted $ PiecePoly $ coef)coef_1002 [1,]<-coef_1002 [1,] + random_quadratic [2,1]coef_1002 [2,]<-coef_1002 [2,] + random_quadratic [2,2] + random_quadratic [2,3]spl_1002_unshifted<-spl_population_unshiftedspl_1002_unshifted $ PiecePoly $ coef<-coef_1002(apv_1002<-求解(spl_1002_unshifted,b = 0,导数= 2))(pv_1002<-预测(spl_1002_unshifted,apv_1002,派生= 1))(apv_pv_1002<-as.data.frame(cbind(apv_1002,pv_1002)))(apv_pv_1002<-apv_pv_1002%&%;%top_n(1,pv_1002)) 

解决方案

注意:OP更新了他的问题,替换了随机行(如 SplinesUtils 时,请确保正确添加系数:

  library(SplinesUtils)spl_population_unshifted<-RegSplineAsPiecePoly(nspline_model,"ns(age,df = 3)",FALSE)#ID = 1001(coef_1001<-spl_population_unshifted $ PiecePoly $ coef)coef_1001 [1,]<-coef_1001 [1,] + random_quadratic [1,1] ## age ^ 0coef_1001 [2,]<-coef_1001 [2,] + random_quadratic [1,2] ## age ^ 1coef_1001 [3,]<-coef_1001 [3,] + random_quadratic [1,3] ## age ^ 2 

然后您可以继续:

  spl_1001_unshifted<-spl_population_unshiftedspl_1001_unshifted $ PiecePoly $ coef<-coef_1001(apv_1001<-求解(spl_1001_unshifted,b = 0,导数= 2))(pv_1001<-预测(spl_1001_unshifted,apv_1001,导数= 1))(apv_pv_1001<-as.data.frame(cbind(apv_1001,pv_1001)))(apv_pv_1001<-apv_pv_1001%&%;%top_n(1,pv_1001)) 


初始答案

这确实令人困惑,但我终于转过头来.我们的代码没有错;我们所看到的在数学上是有保证的.请注意:

主题样条=总体样条+线性线

取二阶导数后,我们就拥有了(因为线性线的二阶导数为0):

主题样条二阶导数=总体样条二阶导数

因此,所有受试者的峰值速度年龄(二阶导数等于0)是相同的!但是,主体之间的峰值速度是不同的.

如果我们希望在峰值速度下得出不同的年龄,则需要模型中的随机二次线而不是随机线.但是建立统计模型并不是数学游戏,因此我们需要三思而后行.

This thread continues with Get subject-specific peak velocity and age at peak velocity values from linear mixed spline models.


I am fitting a linear mixed effects model with a natural spline function for age. I would like to estimate age at peak velocity (apv - years) and peak velocity (pv - grams) for each person in the dataset by differentiating the spline terms. The model includes a random quadratic slope for age.

How can I estimate the person-specific apv and pv? I am using the SplinesUtils package.

Example data:

dat <- structure(list(id = c(1001L, 1001L, 1001L, 1001L, 1001L, 1002L, 
    1003L, 1004L, 1004L, 1004L, 1004L, 1004L, 1004L, 1004L, 1005L, 
    1005L, 1005L, 1005L, 1005L, 1006L, 1006L, 1006L, 1006L, 1006L, 
    1007L, 1007L, 1008L, 1008L, 1008L, 1008L, 1008L, 1009L, 1009L, 
    1009L, 1010L, 1010L, 1010L, 1011L, 1012L, 1012L, 1012L, 1013L, 
    1013L, 1014L, 1015L, 1015L, 1015L, 1016L, 1016L, 1016L, 1016L, 
    1016L, 1017L, 1017L, 1018L, 1020L, 1020L, 1021L, 1021L, 1021L, 
    1021L, 1022L, 1022L, 1023L, 1023L, 1023L, 1023L, 1023L, 1023L, 
    1023L, 1023L, 1023L, 1023L, 1024L, 1024L, 1024L, 1024L, 1024L, 
    1025L, 1025L, 1025L, 1026L, 1026L, 1026L, 1026L, 1027L, 1027L, 
    1028L, 1028L, 1028L, 1028L, 1028L, 1028L, 1028L, 1029L, 1029L, 
    1029L, 1029L, 1029L, 1029L, 1030L, 1030L, 1030L, 1030L, 1030L, 
    1030L, 1030L, 1030L, 1031L, 1031L, 1031L, 1031L, 1032L, 1032L, 
    1032L, 1032L, 1032L, 1033L, 1033L, 1033L, 1033L, 1034L, 1034L, 
    1034L, 1034L, 1034L, 1035L, 1035L, 1036L, 1037L, 1037L, 1037L, 
    1037L, 1039L, 1039L, 1040L, 1040L, 1040L, 1040L, 1040L, 1040L, 
    1041L, 1041L, 1041L, 1041L, 1041L, 1041L, 1042L, 1042L, 1042L, 
    1042L, 1042L, 1042L, 1042L, 1043L, 1043L, 1043L, 1043L, 1044L, 
    1044L, 1044L, 1045L, 1045L, 1045L, 1045L, 1045L, 1045L, 1047L, 
    1048L, 1048L, 1049L, 1049L, 1049L, 1049L, 1051L, 1051L, 1052L, 
    1052L, 1052L, 1052L, 1052L, 1053L, 1053L, 1053L, 1053L, 1053L, 
    1054L, 1054L, 1054L, 1054L, 1054L, 1054L, 1054L, 1054L, 1056L, 
    1056L, 1056L, 1056L, 1057L, 1057L, 1058L, 1058L, 1058L, 1058L, 
    1058L, 1060L, 1060L, 1060L, 1061L, 1061L, 1061L, 1061L, 1061L, 
    1062L, 1062L, 1062L, 1062L, 1062L, 1063L, 1063L, 1063L, 1064L, 
    1064L, 1064L, 1064L, 1065L, 1065L, 1066L, 1066L, 1066L, 1066L, 
    1066L, 1066L, 1067L, 1067L, 1067L, 1068L, 1068L, 1068L, 1068L, 
    1068L, 1068L, 1068L, 1069L, 1070L, 1070L, 1070L, 1071L, 1071L, 
    1071L, 1072L, 1072L, 1072L, 1072L, 1072L, 1073L, 1073L, 1073L, 
    1073L, 1074L, 1074L, 1074L, 1075L, 1075L, 1075L, 1075L, 1075L, 
    1075L, 1076L, 1076L, 1076L, 1077L, 1077L, 1077L, 1077L, 1077L, 
    1077L, 1078L, 1078L, 1078L, 1078L, 1078L, 1078L, 1078L, 1080L, 
    1080L, 1080L, 1080L, 1081L, 1081L, 1082L, 1082L, 1082L, 1083L, 
    1083L, 1084L, 1085L, 1085L, 1085L, 1085L, 1085L, 1085L, 1086L, 
    1086L, 1086L, 1087L, 1087L, 1087L, 1087L, 1087L, 1087L, 1087L, 
    1087L, 1088L, 1088L, 1088L, 1088L, 1089L, 1089L, 1089L, 1089L, 
    1089L, 1090L, 1090L, 1091L, 1091L, 1091L, 1091L, 1091L, 1092L, 
    1092L, 1092L, 1092L, 1092L, 1093L, 1093L, 1093L, 1093L, 1094L, 
    1094L, 1094L, 1094L, 1094L, 1095L, 1095L, 1095L, 1095L, 1096L, 
    1097L, 1097L, 1098L, 1098L, 1098L, 1098L, 1098L, 1099L, 1099L, 
    1099L, 1099L, 1099L, 1099L, 1099L, 1099L, 1100L, 1100L, 1100L, 
    1101L, 1101L, 1101L, 1101L, 1103L, 1103L, 1103L, 1103L, 1103L, 
    1103L, 1103L, 1104L, 1104L, 1104L, 1104L, 1105L, 1105L, 1105L, 
    1106L, 1106L, 1106L, 1106L, 1106L, 1106L, 1106L, 1106L, 1106L, 
    1107L, 1108L, 1110L, 1111L, 1112L, 1117L, 1123L), y = c(1934.047646, 
    1075.598345, 1956.214821, 2000.38538, 2000.38538, 732.315937, 
    3119.86, 624.951231, 791.2764892, 1884.530826, 624.951231, 1047.57, 
    1047.57, 791.2764892, 1238.306103, 1555.042976, 2547.870529, 
    2547.870529, 2467.385, 1181.635212, 1181.635212, 565.306282, 
    2016.027874, 2016.027874, 712.6134567, 635.2537841, 2167.362267, 
    2575.574188, 2167.362267, 2480.028259, 2575.574188, 2875.363243, 
    1180.139938, 2828.037147, 3017.119362, 2722.940933, 2167.92, 
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    442.433671, 1251.627064, 406.2565479, 2108.787437, 983.1101169, 
    2102.085403, 1155.713411, 1909.797131, 2871.55, 2711.07, 2883.22245, 
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    2190.560314, 744.1710777, 1498.981777, 2460.912292, 590.1345787, 
    2487.559135, 1855.601353, 660.9104843, 1116.08, 792.929533, 708.8373737, 
    2272.232933, 1801.729801, 2299.800095, 2272.232933, 2299.800095, 
    1895.828438, 1757.75, 1050.279345, 1757.75, 1326.09478, 1326.09478, 
    1633.119305, 1558, 1167.971405, 1828.16, 1788.571758, 2175.469, 
    1071.039494, 941.6030864, 2053.067215, 1461.02132, 1597.646778, 
    1885.321567, 2195.704372, 2195.704372, 1675.768558, 3157.550789, 
    1565.173126, 2195.704372, 3157.550789, 2404.836883, 2541.045593, 
    585.7223682, 2465.177761, 2678.462074, 500.3733997, 2465.177761, 
    781.342, 898.3551559, 2465.177761, 2465.177761, 1807.02, 1418.888027, 
    1797.36, 1807.02, 2200.06, 2218.369926, 2200.06, 1986.642735, 
    2088.292, 2069.139, 1507.901432, 2061.395798, 2075.164864, 2081.913219, 
    2081.913219, 483.8579493, 1857.88, 2578.772636, 1857.88, 1857.88, 
    1039.632153, 2288.28, 2288.28, 1831.349922, 2349.23, 933.1002788, 
    2626.298935, 1521.744, 933.1002788, 2626.298935, 1984.760715, 
    2450.333, 1732.339031, 1984.760715, 2731.9, 869.2320918, 1785.72, 
    1922.798, 3081.28, 1508.8, 2421.288597, 1922.798, 1268.074959, 
    1569.05, 1808.115, 1569.05, 1268.074959, 2165.724808, 2165.724808, 
    1808.115, 2084.149837, 2693.027184, 2464.489, 2607.653496, 1012.837271, 
    1012.837271, 2673.190872, 2635.290516, 2773.42, 2635.290516, 
    2654.772674, 2377.905655, 2679.014969, 2654.772674, 1226.40016, 
    1470.69, 1273.789799, 2294.926086, 1226.40016, 1470.69, 1273.789799, 
    1873.817, 2274.930534, 2317.429165, 959.1709613, 1328.159428, 
    1328.159428, 1328.159428, 959.1709613, 1630.28, 1610.54982, 2507.05302, 
    750.467966, 750.467966, 821.2255058, 802.8240452, 2829.47879), 
        age = c(31.54004107, 11.95071869, 27.88501027, 27.88501027, 
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Code for fitting the linear mixed spline model:

    library(nlme)
    library(splines)
    library(tidyverse)

    nspline_model <- lme(y ~ ns(age, df = 3), data = dat, random = ~ poly(age, 2) | id)

This is code showing how I tried to calculate apv and pv for two individuals - but i get a negative value for pv, and an apv value of ~39 years

# LIST OF PERSON IDs
dat %>% distinct(id) %>% pull()

library(SplinesUtils)

(random_quadratic <- random.effects(nspline_model))
spl_population_unshifted <- RegSplineAsPiecePoly(nspline_model, "ns(age, df = 3)", FALSE)

# ID = 1001

(coef_1001 <- spl_population_unshifted$PiecePoly$coef) 
coef_1001[1, ] <- coef_1001[1, ] + random_quadratic[1, 1]
coef_1001[2, ] <- coef_1001[2, ] + random_quadratic[1, 2] + random_quadratic[1, 3]

spl_1001_unshifted <- spl_population_unshifted
spl_1001_unshifted$PiecePoly$coef <- coef_1001

(apv_1001 <- solve(spl_1001_unshifted, b = 0, deriv = 2)) 
(pv_1001 <- predict(spl_1001_unshifted, apv_1001, deriv = 1))

(apv_pv_1001 <- as.data.frame(cbind(apv_1001, pv_1001)))
(apv_pv_1001 <- apv_pv_1001 %>% top_n(1, pv_1001))

# ID = 1002

(coef_1002 <- spl_population_unshifted$PiecePoly$coef) 
coef_1002[1, ] <- coef_1002[1, ] + random_quadratic[2, 1]
coef_1002[2, ] <- coef_1002[2, ] + random_quadratic[2, 2] + random_quadratic[2, 3]

spl_1002_unshifted <- spl_population_unshifted
spl_1002_unshifted$PiecePoly$coef <- coef_1002

(apv_1002 <- solve(spl_1002_unshifted, b = 0, deriv = 2)) 
(pv_1002 <- predict(spl_1002_unshifted, apv_1002, deriv = 1))

(apv_pv_1002 <- as.data.frame(cbind(apv_1002, pv_1002)))
(apv_pv_1002 <- apv_pv_1002 %>% top_n(1, pv_1002))

解决方案

Note: OP updated his question, replacing the random line (as used in the previous thread) with a random quadratic after being informed by my initial answer. My answer is then renewed to accommodate that.


New answer

When using a random quadratic, specify it with raw polynomial instead of (the default) orthogonal polynomial, otherwise the resulting polynomial coefficients have a different interpretation.

nspline_model <- lme(y ~ ns(age, df = 3), data = dat,
                     random = ~ poly(age, 2, raw = TRUE) | id)
random_quadratic <- random.effects(nspline_model)

Then when using SplinesUtils, make sure you add coefficients correctly:

library(SplinesUtils)

spl_population_unshifted <- RegSplineAsPiecePoly(nspline_model, "ns(age, df = 3)", FALSE)

# ID = 1001

(coef_1001 <- spl_population_unshifted$PiecePoly$coef) 
coef_1001[1, ] <- coef_1001[1, ] + random_quadratic[1, 1]  ## age ^ 0
coef_1001[2, ] <- coef_1001[2, ] + random_quadratic[1, 2]  ## age ^ 1
coef_1001[3, ] <- coef_1001[3, ] + random_quadratic[1, 3]  ## age ^ 2

Then you can proceed:

spl_1001_unshifted <- spl_population_unshifted
spl_1001_unshifted$PiecePoly$coef <- coef_1001

(apv_1001 <- solve(spl_1001_unshifted, b = 0, deriv = 2)) 
(pv_1001 <- predict(spl_1001_unshifted, apv_1001, deriv = 1))

(apv_pv_1001 <- as.data.frame(cbind(apv_1001, pv_1001)))
(apv_pv_1001 <- apv_pv_1001 %>% top_n(1, pv_1001))


Initial answer

This was indeed puzzling but I finally had my head turned around. There is nothing wrong with our code; what we see is mathematically guaranteed. Note that:

subject spline = population spline + linear line

After taking 2nd derivative, we have (since the 2nd derivative of a linear line is 0):

subject spline 2nd derivative = population spline 2nd derivative

Therefore, the age at peak velocity (where the 2nd derivative hits 0) is identical for all subjects! However, the peak velocity is different between subjects.

If we expect to derive a different age at peak velocity we need a random quadratic rather than a random line in the model. But building statistical model is not a mathematical game, so we need think twice about it.

这篇关于线性混合自然样条模型在峰值速度下的个体年龄的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!

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