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将 mob() 树（partykit 包）与 nls() 模型一起使用

[英]Using mob() trees (partykit package) with nls() model

 原文  2016-05-04 20:29:57  8   1    r/ nls/ party

问题描述

I'm trying to use model-based recursive partitioning (MOB) with the mob() function (from the partykit package) to separate several curves that were derived using the nls() function.我正在尝试使用基于模型的递归分区 (MOB) 和mob()函数（来自partykit包）来分离使用nls()函数导出的几条曲线。 I had to define my model and determine the starting values.我必须定义我的模型并确定起始值。 I've been trying to see if this could be used with the mob() function to no avail.我一直试图看看这是否可以与mob()函数一起使用，但无济于事。

I tried following this example on page 7: https://cran.r-project.org/web/packages/partykit/vignettes/mob.pdf I created a fit function that estimates the starting values and would return the estimates etc. of the nls() .我尝试按照第 7 页上的此示例进行操作： https : //cran.r-project.org/web/packages/partykit/vignettes/mob.pdf我创建了一个拟合函数来估计起始值并返回估计值等nls() 。 But I can't seem to get anything going after that.但在那之后我似乎什么也做不了。 I'd like to know if it is at all possible to use a custom model, with coefficients and both dependent and independent variables and to include them in mob() and get it to work.我想知道是否有可能使用带有系数以及因变量和自变量的自定义模型，并将它们包含在mob()并使其工作。 I tried the lmtree() function but of course this will only give a straight line.我尝试了lmtree()函数，但当然这只会给出一条直线。

My code is below.我的代码如下。 Basically I use a segmented linear regression to get the starting values of a double exponential curve that I am using.基本上，我使用分段线性回归来获取我正在使用的双指数曲线的起始值。 This is the furthest I got basically.这基本上是我得到的最远的。 The parameter estimates give an error etc, if you even get past that it just won't run.参数估计会给出错误等，如果你甚至超过它就不会运行。 I just need to know if it is at possible for the mob() function to run nls() .我只需要知道mob()函数是否有可能运行nls() 。

I loaded sample data, but if it is possible to use the nls()我加载了示例数据，但如果可以使用nls()

    photo.try <- function(y, x,start = NULL, weights = NULL, offset = NULL, estfun = FALSE, object = TRUE) 
        {
            lin.mod1 <- lm(y ~ x)
            segmented.mod.2 <- segmented(lin.mod1, seg.Z = ~x, psi=1)
            segmented.mod1 <- segmented(lin.mod1, seg.Z = ~x, psi =  segmented.mod.2$psi[1,2])
            nls(y ~ (a*exp(-b * x) - c* exp(-d* x)), start = list(a = -1*(intercept(segmented.mod1)[[1]][1,1]) , b = slope(segmented.mod1)[[1]][1,1], 
            c = -1*(intercept(segmented.mod1)[[1]][2,1]), 
            d = -1*slope(segmented.mod1)[[1]][2,1]))

        }

photo_form <- Pn ~ (a*exp(-b * PAR) - c* exp(-d* PAR))| Species


photo_tree <- mob(photo_form, data = eco, fit = (photo.try))

Here is my sample data:这是我的示例数据：

eco <- structure(list(Species = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 4L, 4L, 4L, 4L, 4L, 4L, 
4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 
4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 
4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 
4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 
4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 
4L, 4L, 4L, 4L, 4L, 4L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 
5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 
5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 
5L, 5L, 5L, 5L, 5L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 
6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 
6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 
6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 
6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 
6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 
6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 
6L, 6L, 6L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 
7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 
7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 
7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 
7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 
7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 
7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L), .Label = c("Bogum", 
"Clethra", "Eugene", "Guarria", "Melo", "Santa", "Sapium"), class = "factor"), 
    PAR = c(0, 58.6, 101.4, 228.6, 462.4, 904.7, 1565.8, 1992.1, 
    2395.9, 0, 72.8, 125.9, 232.8, 411, 841.1, 1669.6, 2394.5, 
    2394.9, 0, 53.5, 122.1, 231.6, 451, 808.5, 1575, 2394.6, 
    2395.1, 0, 70.9, 104.8, 251.1, 474.6, 858.3, 1612.3, 2393.3, 
    2395.1, 0, 63.1, 124.6, 277.1, 417.7, 824.4, 1649.6, 2377.7, 
    2381.9, 0, 31, 46.5, 115.7, 228.1, 424.3, 822.5, 1644.2, 
    2380.7, 2381.2, 0, 50.1, 118.1, 203.3, 413.2, 804.5, 1587.3, 
    2385.3, 0, 28.8, 36.9, 101.2, 211.7, 423.1, 793, 0, 43.6, 
    106.7, 200.8, 468.6, 808.4, 1567, 2367.1, 2376.5, 0.1, 40.4, 
    104.1, 202.2, 447.3, 794.7, 1546, 2391.8, 2393.3, 0.1, 44.1, 
    107.5, 227.4, 429.6, 802.5, 1668.4, 2391, 0, 42.2, 125.3, 
    126.2, 127.3, 240.3, 433.4, 791, 1600, 2396.8, 2397, 2399.3, 
    0, 72.7, 118.1, 236.9, 425, 828.4, 1613.3, 1615.4, 2396.1, 
    2396.5, 2397.2, 2397.5, 0, 62, 116.2, 235.5, 401.7, 879, 
    879.8, 1552.2, 1553.9, 2394.3, 2394.4, 2394.7, 2396.6, 0, 
    84.8, 135, 209.8, 425.3, 859.1, 1597.6, 2377.3, 2379.5, 2385.1, 
    0.1, 62, 106.3, 226.2, 442.9, 822.5, 1462.3, 2389.8, 2392.1, 
    0.1, 0.1, 73.9, 126, 249.8, 428.5, 846.5, 1555.3, 2390.1, 
    2390.7, 2390.8, 0, 68.7, 121.5, 209.7, 426.2, 803, 1525.9, 
    2389.8, 0, 52.8, 96.9, 211.1, 441.3, 787.9, 1566.5, 2415.2, 
    2415.3, 2415.5, 2417.5, 2417.7, 2418.5, 0.1, 46.5, 108.4, 
    233.5, 461.7, 792.3, 1635.7, 2415.1, 2415.6, 2415.6, 2416.5, 
    2416.6, 2417.8, 0.1, 68.3, 110, 239.5, 531.7, 847.2, 1591.4, 
    2387.3, 2387.6, 2389.7, 0, 49.7, 114.6, 230.6, 397.7, 398.2, 
    817.7, 1596.4, 2376.2, 2376.4, 2380.9, 0, 62.9, 65.5, 117, 
    209, 431.2, 854.5, 1611.3, 2387.3, 2388.5, 2390.3, 0, 49.1, 
    108.9, 200.3, 408.8, 842.2, 1630.2, 2386.5, 2386.8, 2388.2, 
    0, 64.8, 122.9, 226, 422.9, 801.6, 1635.7, 2383.6, 2383.6, 
    2384.3, 2386.1, 0, 36.7, 143.2, 213.7, 444.9, 814.9, 816.2, 
    1496.5, 2384.7, 2386.5, 2388.6, 0.1, 45.6, 105.2, 206.7, 
    494.8, 901.2, 1610.9, 2388, 2388.1, 2388.3, 2388.6, 0, 0.1, 
    45.9, 48.5, 100.2, 209.4, 432.4, 778, 1600.3, 2408.8, 2408.8, 
    0, 71.8, 121.6, 216.4, 404.3, 815.2, 1622, 2414.9, 2415.1, 
    2416.1, 2416.1, 0, 36.2, 97.5, 186.7, 417.9, 840.4, 1597.5, 
    2390.7, 2390.9, 2391.2, 2391.2, 2391.5, 2392.1, 2392.5, 0, 
    53.8, 138.2, 227, 403.6, 800.8, 1642.3, 2396.9, 2397.1, 0, 
    57.9, 95.1, 246.6, 466.8, 796.2, 1574.2, 2395.5, 2397.3, 
    0, 54.9, 94.9, 201.7, 408.1, 822.6, 1596, 2384.1, 0, 55.6, 
    131, 202.5, 419.8, 798.5, 1614, 2387.4, 2387.8, 0, 39.1, 
    109.6, 197.1, 403.3, 835.4, 836.9, 1725.9, 1727.4, 1729.3, 
    1730.6, 54.5, 58.6, 125.4, 226.9, 409, 806.8, 1578.8, 2377.2, 
    2380.1, 2388.3, 0, 68, 127.4, 206.9, 510.5, 814.9, 1561, 
    2404.1, 2404.8, 0, 58.4, 95.3, 229.6, 457.2, 781.5, 1634.4, 
    2399.8, 2401, 2403, 0.1, 56.5, 101.9, 221.8, 394.3, 815.1, 
    1655.4, 2411.8, 2411.9, 0, 50.2, 107.3, 220.5, 434.4, 819.8, 
    1630.6, 2412.4, 2412.6, 0, 48.4, 117.7, 195.3, 403.2, 801, 
    1632.7, 2388.9, 2389.3, 2390.7, 0, 50.4, 120.3, 234.7, 460.3, 
    829.1, 1581.7, 2398.5, 2402.3, 0, 60.8, 105.8, 215.8, 466.6, 
    826, 828.3, 1570.8, 2405.6, 2406.1, 2408.8, 0, 52.6, 106.9, 
    206.5, 414.3, 868.4, 1629.9, 1655.1, 2409.1, 2413, 0, 49.5, 
    100.6, 232.9, 389.4, 808.2, 1588.2, 2412.4, 2413.3, 2415.9, 
    0.1, 70.9, 110.5, 208.4, 409, 807.5, 1579.9, 2382.2, 2382.5, 
    2383.6, 2383.8, 0, 61.5, 106.5, 213.9, 473.8, 814.2, 1561.9, 
    2390.7, 2391.9, 2393.1, 0, 59.9, 64, 112, 216, 397.6, 807.4, 
    1625, 2392.3, 2395.1, 0, 74, 108.8, 109.7, 236.1, 433.6, 
    794.7, 1590.3, 2381.9, 2382.5, 0.1, 56.3, 114.5, 254.1, 487.7, 
    864.3, 1593.5, 2369.3, 2369.3, 2372.3, 2373.9, 0.2, 57.1, 
    110, 201.4, 402.7, 807.2, 1572.9, 2392.8, 2393.5, 0.1, 56.4, 
    122.5, 224.5, 420.2, 853.7, 1502.1, 2390.3, 2392.9, 0, 50.5, 
    53.7, 118.2, 230, 462.8, 794.3, 1513.4, 2391.4, 2392.3, 2393.4, 
    2393.4, 2394.1, 0.1, 49.7, 98.3, 208.3, 383.2, 850.7, 1653.5, 
    2395.3, 2396, 2397.1, 0, 48.4, 121.2, 228.8, 423.9, 817, 
    1708.5, 2389.9, 2389.9, 0, 66.4, 129.7, 209.4, 431.5, 794.1, 
    1673.7, 2383.7, 2384.2, 0, 57, 122.6, 215, 434.1, 838.5, 
    1657.5, 2386.4, 0.1, 22.6, 127.8, 220.4, 404.3, 810.9, 1592.3, 
    2386.7, 2388.7, 0, 49.8, 119.7, 200.5, 463.8, 828.7, 1560.7, 
    2384.5, 2385.7, 2391.2, 0, 73.1, 138.2, 226.6, 408.5, 815.3, 
    1627.3, 2390.2, 2395.4, 0, 61.2, 108.8, 233.8, 417.7, 824.5, 
    1502.7, 2395, 2396.2, 0, 56, 101.4, 226.3, 282.1, 412.9, 
    873.8, 1672.6, 2380.4, 2380.9, 2381.5, 0.1, 70.7, 138, 246, 
    444.4, 817.1, 1643.2, 2391.5, 2391.8, 2392), Pn = c(-0.95, 
    0.75, 0.94, 1.27, 1.5, 1.9, 2.14, 2.35, 2.38, 1.48, 3.51, 
    3.7, 3.99, 4.4, 4.32, 4.52, 4.73, 4.72, 1.97, 3.24, 4.23, 
    4.35, 4.41, 4.66, 4.57, 4.68, 4.88, 1.16, 3.64, 4.05, 4.75, 
    5.42, 5.57, 5.55, 5.89, 5.8, 1.48, 3.89, 4.7, 5.34, 5.47, 
    5.62, 5.71, 5.7, 6.08, 1.26, 0.59, 2.96, 4.34, 5, 4.82, 5.22, 
    5.2, 5.33, 5.51, 1.2, 2.95, 3.67, 3.9, 4.06, 4.59, 4.6, 4.62, 
    2.01, 1.92, 2.41, 2.19, 2.22, 2.41, 2.21, 1.6, 3.29, 3.97, 
    4.39, 4.89, 5.12, 4.93, 5.12, 5.1, 2.39, 3.84, 4.45, 4.63, 
    4.43, 4.93, 4.78, 4.73, 5.04, 3.09, 3.74, 4.03, 3.89, 4.52, 
    4.43, 4.24, 4.26, 1.5, 2.73, 2.83, 3.14, 2.89, 3.39, 2.89, 
    2.84, 3.34, 3.11, 3.16, 3.31, 0.1, 1.17, 1.72, 1.61, 1.64, 
    2.06, 2.17, 1.99, 2.31, 2.14, 2.27, 2.08, 0.17, 1.17, 1.32, 
    1.33, 1.4, 1.8, 1.48, 2, 1.81, 1.95, 2.09, 1.73, 1.85, 2.95, 
    4.33, 4.82, 4.98, 4.97, 5.03, 5.08, 5.22, 5.32, 4.88, 2.17, 
    3.08, 3.32, 3.42, 3.45, 3.67, 3.64, 3.71, 3.71, 2.85, 2.33, 
    3.15, 2.81, 3.22, 2.99, 3.16, 3.33, 3.56, 3.61, 3.63, 2.52, 
    3.55, 4.07, 4.1, 4.17, 4.41, 4.53, 4.56, 2.06, 2.57, 2.91, 
    2.61, 3.08, 3.29, 3.99, 6.49, 5.23, 6.08, 5.74, 4.41, 6.5, 
    1.59, 3.22, 3.59, 3.75, 3.84, 4.5, 4.93, 6.87, 6.75, 6.97, 
    6.53, 6.04, 6.82, 1.28, 3.56, 4.39, 5.27, 5.51, 6.38, 7.05, 
    7.46, 7.16, 7.24, 0.87, 2.45, 3.86, 4.32, 4.57, 4.43, 4.68, 
    4.71, 4.86, 4.36, 4.68, 1.06, 2.79, 4.05, 4.86, 5.48, 5.9, 
    6.38, 6.79, 7.46, 7.12, 7.03, 2.76, 3.92, 3.96, 4.07, 4.2, 
    4.5, 4.91, 5.52, 5.49, 5.33, 2.84, 4.78, 4.83, 4.76, 4.74, 
    4.84, 5.19, 5.59, 5.74, 5.7, 5.65, 3.02, 3.61, 4.14, 4.23, 
    4.45, 4.37, 4.5, 4.6, 4.78, 4.79, 4.85, 2.71, 4.26, 5.42, 
    6.24, 6.58, 6.63, 6.55, 7.29, 7.43, 7.24, 7, 3.36, 2.19, 
    2.86, 2.87, 2.37, 3.16, 2.68, 3, 3.4, 3.6, 4.35, 1.28, 2.62, 
    2.92, 3.3, 3.35, 3.58, 3.73, 4.02, 4, 3.7, 3.75, 1.61, 2.26, 
    2.5, 2.52, 2.71, 2.61, 2.75, 3.19, 2.92, 3.99, 4.36, 3.67, 
    4.14, 4.37, -0.28, 1.91, 2.78, 2.84, 2.96, 3.04, 3.24, 3.44, 
    3.58, 1.78, 4.12, 4.58, 4.33, 4.8, 4.7, 5.02, 5.09, 5.22, 
    2.79, 4.71, 4.89, 4.93, 4.87, 4.92, 4.83, 4.81, 1.66, 3, 
    4.04, 4.35, 4.56, 4.75, 4.75, 4.66, 4.89, 1.56, 2.77, 3.86, 
    3.58, 3.7, 3.76, 3.58, 4.55, 4.63, 4.05, 3.73, 1.76, 2.71, 
    2.98, 3.01, 3.06, 3.22, 2.99, 3.15, 3.32, 3.34, 1.58, 3.76, 
    4.97, 5.21, 5.29, 5.5, 5.59, 5.71, 5.74, 1.89, 2.67, 3.01, 
    3.14, 3.39, 3.57, 3.45, 3.91, 4.11, 3.94, 1.15, 2.88, 3.63, 
    4.32, 4.09, 4.43, 4.58, 4.61, 4.63, 1.23, 2.26, 3.15, 3.33, 
    3.3, 3.61, 3.46, 3.65, 3.67, 0.19, 2.23, 3.43, 4.1, 4.85, 
    5.21, 5.8, 6.27, 6.34, 6.08, 1.94, 3.72, 4.88, 5.51, 6.71, 
    6.51, 6.96, 7.01, 7.4, 0.48, 2.29, 2.5, 2.87, 3.18, 3.51, 
    3.13, 3.86, 4.13, 4.34, 4.03, 1.63, 3.64, 5.15, 5.95, 6.43, 
    6.57, 6.61, 6.51, 6.65, 6.56, 1.93, 3.95, 4.63, 5.66, 6.03, 
    6.28, 6.67, 6.69, 6.95, 6.75, 0.93, 3.14, 3.46, 3.9, 4.19, 
    4.27, 4.77, 5.39, 5.36, 5.24, 5.02, 1.71, 3.31, 3.86, 4.02, 
    4.02, 4.29, 4.36, 4.73, 4.88, 4.59, 1.63, 2.65, 2.63, 2.48, 
    2.93, 3.45, 4.01, 4.67, 5.02, 5.08, 1.93, 3.54, 3.8, 3.81, 
    4.04, 4.17, 4.38, 4.55, 4.99, 4.99, 1.29, 2.73, 3.32, 3.66, 
    3.77, 3.79, 4.14, 4.37, 4.22, 4.1, 4.14, 1.06, 2.89, 3.65, 
    4.01, 4.11, 4.19, 4.66, 5.03, 5.12, 0.97, 2.45, 2.99, 3.32, 
    3.34, 3.35, 3.47, 3.12, 3.38, 2.29, 1.72, 4.33, 5.49, 6.44, 
    6.96, 7.91, 7.49, 8.45, 8.21, 8.17, 8.71, 8.35, 0.29, 2.99, 
    3.93, 4.52, 5.69, 6.23, 6.23, 6.81, 6.96, 6.68, 0.99, 3.67, 
    4.62, 5.52, 5.86, 6.23, 5.91, 6.64, 6.29, -0.08, 3.34, 4.89, 
    6.02, 6.37, 6.59, 6.99, 6.95, 7.2, 0.99, 2.28, 2.72, 2.67, 
    2.99, 3.18, 3.55, 3.58, 1.31, 2.18, 5.55, 7.37, 8.42, 9.14, 
    9.44, 9.26, 9.5, 1.23, 3.11, 5.01, 6.21, 7.14, 7.44, 7.79, 
    7.73, 8.1, 7.96, 1.35, 3.33, 5.67, 6.58, 7.05, 7.36, 7.73, 
    7.75, 7.99, 0.4, 2.25, 2.83, 3.31, 3.55, 3.66, 3.96, 3.54, 
    3.77, 1.46, 2.91, 3.51, 3.64, 4.5, 3.83, 3.96, 4.17, 4.66, 
    4.09, 4.44, 2.41, 4.77, 5.49, 6.05, 6.15, 6.28, 6.6, 6.76, 
    6.75, 6.78)), .Names = c("Species", "PAR", "Pn"), class = "data.frame", row.names = c(NA, 
-628L))

1 个解决方案

解决方案1
 2 已采纳  2016-05-05 20:37:07

Yes, we can!我们可以！ ;-) ;-)

In principle, you were attempting to do the right thing but a few aspects were not quite correct.原则上，您正在尝试做正确的事情，但有几个方面不太正确。 The main issue is how you pass around the data and the formula: As mob() does not know anything about the way nls() specifies its formulas, a plain formula Pn ~ PAR | Species主要问题是如何传递数据和公式：由于mob()对nls()指定其公式的方式一无所知，因此简单的公式Pn ~ PAR | Species Pn ~ PAR | Species needs to be used and then the fit function needs to know what to do with the data.需要使用Pn ~ PAR | Species ，然后fit函数需要知道如何处理数据。 The pre-processing offered by mob() can either set up a model matrix (with intercept, dummy/contrast codings, etc.) or a model frame (where factors are still factors etc.). mob()提供的预处理可以设置模型矩阵（具有截距、虚拟/对比度编码等）或模型框架（其中因素仍然是因素等）。 In this case it is easiest to use the default model matrix and then to omit the intercept in the fitting function.在这种情况下，最容易使用默认模型矩阵，然后在拟合函数中省略截距。

The second problem with your code was that you used the extended specification of the fit function (with estfun and object arguments) but only supplied the fitted model object.您的代码的第二个问题是您使用了fit函数的扩展规范（带有estfun和object参数），但只提供了拟合的模型对象。 With that specification mob() expects that the fit function sets up a suitable list with coefficients and objfun etc.有了这个规范， mob()期望fit函数设置一个合适的列表，其中包含coefficients和objfun等。

In combination, this means that your fit function should look like this:结合起来，这意味着您的fit函数应如下所示：

photofit <- function(y, x = NULL, start = NULL, weights = NULL, offset = NULL, ...,
  estfun = FALSE, object = FALSE)
{
  ## only use first real regressor (without intercept)
  x <- x[, 2]

  ## obtain starting values if necessary
  if(is.null(start)) {
    aux_lm <- lm(y ~ x)
    aux_seg_2 <- segmented::segmented(aux_lm, seg.Z = ~ x, psi = 1)
    aux_seg_1 <- segmented::segmented(aux_lm, seg.Z = ~ x, psi = aux_seg_2$psi[1, 2])
    start <- list(
      a = -1 * (segmented::intercept(aux_seg_1)[[1]][1, 1]),
      b =           segmented::slope(aux_seg_1)[[1]][1, 1], 
      c = -1 * (segmented::intercept(aux_seg_1)[[1]][2, 1]), 
      d = -1 *      segmented::slope(aux_seg_1)[[1]][2, 1]
    )
  } else {
    start <- as.list(start)
  }

  ## estimate NLS model
  rval <- nls(y ~ (a * exp(-b * x) - c * exp(-d * x)), start = start)

  ## return processed information for mob()
  list(
    coefficients = coef(rval),
    objfun = deviance(rval),
    estfun = if(estfun) sandwich::estfun(rval) else NULL,
    object = if(object) rval else NULL    
  )
}

And then you can grow the MOB tree.然后你可以种植 MOB 树。 Specifying the verbose = TRUE control option will give you a little bit of progress information while you wait:指定verbose = TRUE控制选项将在您等待时为您提供一些进度信息：

photomob <- mob(Pn ~ PAR | Species, data = eco, fit = photofit,
  control = mob_control(verbose = TRUE))
coef(photomob)
##           a             b         c             d
## 4  2.967680 -3.216708e-05  1.519680  1.076879e+01
## 5 -1.811596  1.967366e-02 -3.573079 -4.877852e-05
## 6 -2.772783  1.438087e-02 -4.177953 -7.821814e-05
## 8 -2.427253  1.757744e-02 -4.449105 -1.328930e-04
## 9 -4.579248  1.020021e-02 -5.714575 -7.502393e-05

You can then also visualize the tree.然后，您还可以将树可视化。 By default a numeric summary is shown in each node but you can also easily display the fitted curves:默认情况下，每个节点中都会显示数字摘要，但您也可以轻松显示拟合曲线：

plot(photomob)
plot(photomob, terminal_panel = node_bivplot, tnex = 2)

photomob 可视化 1

Photomob 可视化 2

As you see the tree selected five terminal nodes with different parameters.如您所见，树选择了五个具有不同参数的终端节点。 I would recommend that you do some more diagnostics on the model fits in the different nodes because I'm not sure how well all parameters are identified.我建议您对适合不同节点的模型进行更多诊断，因为我不确定所有参数的识别情况。 I'm not very familiar with NLS and might be completely wrong but it seems that not always all parameters can be reliably determined.我对 NLS 不是很熟悉，可能完全错误，但似乎并非总是可以可靠地确定所有参数。

As one illustration I do the following: I extract all nine fitted nls objects from the tree.作为一个例子，我执行以下操作：我从树中提取所有九个拟合的nls对象。 For the model from the root node (node 1) I compute the gradient by summing over all observation-wise gradient contributions (as computed by the estfun() method):对于来自根节点（节点 1）的模型，我通过对所有观测梯度贡献（由estfun()方法计算estfun()求和来计算梯度：

photonls <- refit.modelparty(photomob)
library("sandwich")
colSums(estfun(photonls[[1]]))
##             a             b             c             d 
##  2.010552e-05  5.753230e-02 -1.166331e-04  6.771585e+00

The gradients of parameters ac are reasonably close to zero but for d it isn't.参数 ac 的梯度相当接近于零，但对于 d 则不然。 This may also affect the inference in mob() which is based on the observation-wise gradient contributions (aka model scores or estimating functions).这也可能影响mob()中基于观察梯度贡献（又名模型分数或估计函数）的推理。

In short: What you want to do, can be done!总之：你想做的，都能做到！ But I would recommend considering a simpler model.但我建议考虑一个更简单的模型。 If you do, you just need to modify the photofit() function accordingly and run it through mob() again.如果你这样做了，你只需要相应地修改photofit()函数并再次通过mob()运行它。

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