Sfrgttk

I am trying to find a suitable distribution to describe my data, and as one of the first few steps I created a Cullen and Frey Graph using the descdist command from the fitdistrplus package in GNU R:

library("fitdistrplus")

descdist(df$data, boot=1000)

The data describes the curvature on a point of a surface, with the different observations coming from equivalent points on different objects. Here is the plot for some point on the objects:

For most of the points on the surface, the plot looks very similar to the one shows above (note the bootstrapped points in yellow). However, for certain points it looks quite different, like this:

I would like to know how to interpret this pattern of the bootstrapped points. What does it tell me?

Visual inspection of the atypical points suggests they are in the area where the curvature is almost zero, in case that helps.

Here is my data (output of dput(df$data)) for the upper plot:

c(-0.00076386, 0.045336, 0.014051, -0.041787, 0.023339, 0.014239, 

0.0092057, 0.0084301, 0.020943, 0.01019, -0.0028119, -0.016991, 

-0.00098921, -0.033097, 0.0016237, 0.0012549, 0.0019851, 0.016966, 

-0.00068282, 0.0061208, 0.0029958, 0.018494, 0.00025555, -3.0299e-05, 

-0.00091132, 0.014321, 0.0073784, 0.01479, 0.023929, -0.0063367, 

0.0025699, 0.015087, 0.0014208, 0.001467, -0.00020386, 0.0037273, 

-0.014093, 0.0011921, -0.014109, 0.022459, 0.0078118, -0.00022082, 

0.0010377, 0.001418, 0.0010154, 0.0028933, 0.0019557, 0.0057984, 

-0.0008368, 0.0026886, -0.0050151, -0.0012167, 0.0030177, 0.010013, 

0.022312, -0.001848, -0.012818, -0.00043589, 0.0053455, 0.0032089, 

0.0032384, 0.011193, 0.017151, -0.0066761, -0.0025546, 0.01298, 

-0.0042231, 0.0024245, 0.0015398, 0.013608, 0.0039484, 0.00081566, 

0.01092, 0.011098, 0.0075705, 0.0038331, 0.014112, 6.1992e-05, 

0.003862, 0.0085052, 0.010609, -0.00041915, -0.0046417, -0.00064619, 

-0.032221, 0.0043921, 0.0028192, -0.00086485, -0.0062318, -0.011283, 

0.027339, 0.0033532, 0.011519, 0.0073512, -0.0017631, 0.0023497, 

0.0051281, 0.0046738, 0.0057097, -0.0011277, 0.11261, -0.0027572, 

0.0050015, 0.0089537, 2.4617e-07, 0.0025699, -0.0086815, -0.0050313, 

-0.033569, -0.0158, 0.0045544, 0.016692, 0.00051091, -0.013249, 

0.0030051, 0.0026081, 0.004686, 0.00019892, -0.0039485, -0.0079521, 

0.0012888, 0.012825, -0.0047024, -0.009024, 0.0023051, -0.0046861, 

0.0039009, -0.0024666, -0.00042277, -0.0023346, -0.0011262, 0.0013752, 

-1.813e-05, -0.011235, 0.00092171, 0.0025105, 0.0029965, 0.010461, 

0.0051702, -0.0021151, -0.015144, 0.00026214, 0.032263, 0.0077962, 

0.012388, -0.0034825, -0.014544, -0.0013833, -0.00096014, -0.0069078, 

-3.981e-05, 0.00030865, -0.014931, -1.7708e-05, -0.0061038, 0.0012174, 

-0.0024902, -0.0014924, 1.0677e-05, 0.00043018, 0.0050422, 0.021948, 

0.0097848, 0.0016898, -0.025803, 0.010538, 0.020389, 0.0071247, 

0.0089641, -0.0063912, 0.0029227, -0.023798, -0.005529, -0.01055, 

-0.00035134, -0.00039021, -0.010132, 0.0026251, 1.1334e-05, 0.0049617, 

-0.00043359, 0.015602, 0.0031481, 0.0011061, 0.033732, 0.03997, 

0.0037297, 0.025704, -0.0081762, 0.003853, 0.01115, 0.0033351, 

0.0035474, 0.0050837, 0.0055254, -0.012532, 0.0032077, 0.0012311, 

0.028543, -0.0077595, -0.017084, 0.0022539, 0.016777, -0.0045712, 

0.050084, 0.0015685, -0.011741, 0.0010876, 0.0106, -0.0033016, 

5.8685e-05, 0.007614, -0.012613, 0.010031, 0.0058827, 0.019654, 

0.0011954, 0.00053537, -0.0059612, 0.057128, 0.0035003, -0.0047389, 

0.010864, -0.0020918, 0.0034695, 0.0071228, -0.0094212, 0.01368, 

0.0031702, -0.003895, 0.0009593, -0.010492, 0.001612, 0.0032088, 

-0.0077312, 0.016688, 0.00012541, -0.0067579, -0.0054365, 0.0021638, 

0.0095235, 0.17428, 0.0084727, 0.010209, -0.020409, 0.022679, 

0.0095846, -0.00041361, 0.0059134, 0.0043463, -4.8011e-05, 0.0003717, 

-0.017807, -0.0085258, 0.013516, -0.011611, -0.0012556, 0.0057282, 

-0.00029204, 0.0040735, 0.0079601, 0.0029876, 0.14456, -3.5497e-05, 

-0.0016229, -0.00142, 0.0024437, -0.0019965, 0.0047731, -0.0069031, 

-0.0024837, -0.0063217, -0.0037023, -0.0011777, 0.014164, 0.032929, 

0.0012199, -0.006876, -0.0033327, -0.0049642, 0.00033994, -0.019737, 

-0.0006757, -0.010813, 0.0039238, -0.0033379, -0.01205, -0.014741, 

0.0008597, 0.00086404, 0.020482, -0.0071236, 0.0081256, 0.01513, 

-0.0052792, -0.017796, 3.7647e-05, -0.0011636, 0.0039913, 0.021583, 

-0.010653, -0.0020395, 0.011516, 0.0026764, 0.018921, 0.015807, 

-0.00035428, 0.0025714, 0.0074256, -0.0079076, 0.00064029, -0.001052, 

-0.0049469, 0.007442, -0.012999, 0.011805, 0.0020448, -9.4241e-05, 

-0.0035942, 0.010951, -0.0042067, -0.00011169, -0.0010933, -0.0042723, 

-6.3584e-05, -0.027255, 0.088819, 0.0018361, 0.013476, 0.0071269

)

And here for the lower:

c(-0.014512, -0.0058534, 0.0087152, -0.0078163, 0.056314, 0.029747, 

-0.052597, -0.012501, -0.0036789, -0.014999, -0.012793, -0.044215, 

-0.021863, 0.0087065, -0.011399, -0.019325, 0.013824, 0.0095986, 

-0.004078, -0.014264, -0.011927, 0.0011146, -0.0038653, 0.018538, 

-0.0041803, -0.0099991, -0.025937, 0.023628, -0.0075893, -0.0151, 

-0.0097623, -0.060885, 0.0074398, -0.023108, -0.02431, 0.059038, 

-3.2965e-06, 0.017071, 0.043786, -0.010216, -0.0066353, 0.0027318, 

-0.019151, 0.0047186, -0.051626, -0.00012959, -0.01279, -0.013684, 

0.00094597, 0.014003, 0.01486, -0.037267, -0.014702, -0.01956, 

-0.010359, -0.01508, -0.029832, -0.010463, -9.8748e-05, 0.0088553, 

-0.0025825, -0.04585, 0.0017103, 0.0010617, -0.014712, -0.058952, 

-0.018465, -0.0086677, -0.090302, -0.012687, 0.031989, -0.0010789, 

0.0011435, -0.0052397, -0.028672, -0.00047859, 0.0072699, 0.01623, 

-0.04801, -0.022326, -0.0015933, -0.038886, -0.025243, -0.0022138, 

0.0010459, -0.0057455, -0.019607, 0.0041099, -0.015831, -0.0012497, 

-0.14231, 0.0040444, 0.0073692, -0.0049665, 0.0095247, 0.035928, 

-0.026798, 0.0020477, 0.0020694, 0.0068247, -0.017784, -0.044672, 

-0.054571, -0.0030117, -0.031704, -0.0097623, -0.0066902, -0.075524, 

-0.0047395, -0.021042, 0.079442, 0.032306, 0.021644, -0.0014506, 

-0.011429, -0.038478, -0.010556, -0.014817, -0.0074413, 0.012451, 

-0.02684, 0.0054708, -0.02627, -0.024904, 0.011484, -0.0014307, 

-0.0028452, -0.03075, 0.00027497, -0.03346, 0.026292, 0.0030234, 

0.0058075, -0.019708, -0.012555, -0.016345, -0.03254, 0.034036, 

-0.046767, 0.0074342, -0.00068815, -0.014836, -0.024488, 0.0046096, 

-0.042042, -0.0046255, -0.021847, -0.0064215, 0.012622, -0.0026051, 

-0.057209, 0.038872, -0.016165, 0.015988, 0.016275, -0.016162, 

-0.015021, 0.020844, -0.014098, 0.0031134, 0.00099532, -0.017317, 

-0.063793, 0.0018859, 0.01971, -0.032403, -0.0024375, -0.00073467, 

-0.0074275, -0.00087284, 0.0083021, 0.014111, -0.018832, -0.00083409, 

0.00065538, -0.024792, -0.017424, 0.018622, -0.012342, -0.024214, 

-0.00038098, 0.0056994, -0.021689, -0.063995, 0.012623, -0.0038429, 

-0.078226, -0.01671, -0.0069796, -0.014817, -0.029802, 0.0042582, 

0.001967, 0.0011492, -0.0015149, 0.0071541, -0.014131, -0.042844, 

-0.019941, -0.02201, -0.0035923, -0.012501, 0.00031213, -0.0012541, 

-0.0075098, -0.047008, -0.026675, -0.021419, -0.010504, 0.0018293, 

-0.032401, 0.011153, -0.00094015, -0.031386, -0.031001, 0.0019511, 

-0.012967, -0.012911, 0.0074449, 0.0052992, 0.069074, -0.022406, 

-0.0028998, -0.0037614, 0.019345, -0.032463, -0.030929, 0.0098452, 

-0.01751, -0.018875, -0.015721, -0.003342, -0.01194, -0.005254, 

-0.054454, 0.073446, 2.9542e-05, -0.060855, 0.01012, -0.049511, 

-0.01284, -0.014399, 0.019037, -0.03636, -0.034068, -0.012705, 

-0.03571, -0.018263, -0.0059382, -0.022954, 0.013382, -0.095539, 

0.0086911, -0.038144, 0.074835, -0.019483, -0.032716, -0.0025377, 

-0.0099221, -0.0057603, 0.018333, 1.3211, 0.020368, 0.041849, 

-0.064433, 0.0017635, 0.023663, -0.0012425, -0.13279, 0.017999, 

0.031229, 0.058787, -0.037184, -0.016621, 0.011081, 0.011349, 

0.0026947, 0.019077, 0.0051954, -0.036936, 0.0045157, -0.023299, 

-0.054993, -0.031168, -0.06061, -0.0086002, -0.045094, -0.019699, 

-0.0025394, 0.021987, -0.05349, -0.008101, -0.0074635, -0.010358, 

-0.068063, 0.013118, 0.013409, -0.018069, 0.0015969, -0.00024499, 

0.016927, -0.011481, -0.0053067, 0.0024216, 0.012565, -0.0011296, 

0.017863, -0.073312, 0.092955, -0.034487, -0.031434, -0.007217, 

-0.038946, -0.0070417, -0.11002, 0.069496, -0.0079777, -0.050645, 

-0.0062267, 0.070627, 0.044814, -0.0028551, -0.013993, -0.0094418, 

0.037753, -0.0071857, -0.014971, -0.0021806, -0.046116, -0.00089069

)

[My previous answer had a fatal mistake in it, so I deleted it and made a new one.]

Here's a more basic plot instead of your fancy plot. The black line is the density plot your first dataset, and the red line is of your second. Note that your first dataset shows 4 or 5 discrete points out in the right tail, which could be scanning artifacts. Your second dataset has a bulge in its right tail and then doesn't have the discrete points that your first dataset has.

Do you know how your data is captured? For example, are you scanning objects with software that places points farther apart in areas of low curvature? (For example, are your objects captured as quadrangles, with adjacent quadrangles that have a low angle between them joined into a single quadrangle? Or does is your capture process driven by changes in reflectivity -- i.e. curvature -- that must exceed a threshold before a data point is recorded?)