Given a set of random numbers drawn from a continuous univariate distribution, find the distribution

Question

Given a set of real numbers drawn from a unknown continuous univariate distribution (let's say is is one of beta, Cauchy, chi-square, exponential, F, gamma, Laplace, log-normal, normal, Pareto, Student's t, uniform and Weibull) ..

x <- c(7.7495976,12.1007857,5.8663491,9.9137894,11.3822335,7.4406175,8.6997212,9.4456074,11.8370711,6.4251469,9.3597039,8.7625700,10.3171063,8.0983110,11.7564283,11.7583461,7.3760516,14.5713098,14.3289690,12.8436795,7.1834376,12.2530520,8.9362235,11.8964391,5.4378782,7.8083060,0.1356370,14.9341847,6.8625143,9.0285873,10.2251998,10.3348486,7.7518365,2.8757024,9.2676577,10.6879259,11.7623207,14.0745924,9.3478318,7.6788852,9.7491924,14.9409955,11.0297640,8.5541261,8.6129808,9.2192320,12.3507414,8.9156903,11.6892831,10.2571897,11.1673235,10.5883741,8.2396129,7.3505839,3.4437525,8.3660082,10.5779227,8.5382177,13.6647484,9.0712034,4.1090454,13.4238382,16.1965937,14.2539891,14.6498816,6.9662381,12.3282141,10.9628268,10.8859495,11.6742822,12.0469869,9.1764119,4.2324549,12.6665295,10.7467579,6.4153703,10.3090806,12.0267082,9.2375369,13.8011813,13.0457227,14.0147179,6.9224316,7.1164269,10.7577799,8.0965571,13.3371566,14.6997535,8.8248384,8.0634834,10.2226001,8.5112199,8.1701147,8.1970784,10.5432878,5.9603389,6.6287037,13.3417943,3.1122822,10.4241008,11.4281520,9.4647825,10.5480176,14.2357819,9.4220778,9.7012755,10.9251006,5.3073151,10.8228672,12.0936384,8.5146227,8.4115865,7.7244591,7.2801474,7.3412563,4.5385940,7.8822841,12.7327836,11.5509252,13.0300876,10.0458138,11.3862972,11.3644867,12.6585391,5.8567192,9.8764841,7.6447620,8.7806429,9.2089114,9.1961781,7.2400724,14.7575303,8.6874476,4.6276043,14.0592724,10.3519708,8.2222625,8.7710501,8.5724602,11.4279232,9.6734741,12.1972490,10.1250074,4.8571327,8.0019245,9.8036286,17.7386541,10.8935339,4.7258581,14.2681556,7.4236474,9.4520797,9.2066764,7.7805317,0.4938756,13.0306624,8.0225287,11.1801478,8.7481126,16.5873192,6.0404763,9.5674318,10.8915023,13.2473727,5.5877557,1.4474869,10.9504070,10.8879749,10.7765684,9.1501230,11.0798794,10.0961631,9.5913525,14.0855129,7.3918195,16.6303158,9.1436327,11.9848346,11.4691572,16.0934172,13.1431040,8.2455786,10.7388841,13.7107201,9.6223990,7.6363513,9.5731838,7.0150930,14.1341888,7.5834625,13.8362695,12.9790060,10.4156690,6.4108920,6.3731019,6.3302824,8.4924571,11.2175143,11.6346609,6.0958761,12.8728176,10.2689647,9.7923411,11.3962741,7.3723701,8.1169299,9.7926014,8.7266379,10.7350973,12.7639103,7.4425159,15.9422109,9.9073852,6.2421614,5.2925668,9.9822059,13.9768971,9.3481404,6.8102106,12.6482884,9.8595946,12.8946675,6.3519119,9.2698768,4.9538608,13.8062408,14.7438135,8.5583994,12.4232260,9.4205371,13.6507205,11.7807767,10.9747222,15.9299602,10.0202244,11.9209419,12.8159324,7.0107459,7.8076222,8.0086965,14.7694984,6.4810687,6.6833260,3.9660939,16.2414479,9.3474497,10.2626126,11.7672786,10.1245905,2.3416774,9.2548226,12.3498943,9.1731074,8.6703280,3.8079927,12.0858349,11.1027140,11.9034505,11.1981903,9.5554276,11.5333311,4.1374535,7.9397446,10.6732513,5.4928081,5.9026714,7.1902350,7.3516027,9.5251792,12.8827838,8.6051567,9.9074448,4.7244414,9.4681156,17.4316786,15.0770196,7.4215510,7.2839984,8.2040354,11.2938556,12.2308244,17.2933409,5.7154747,9.9383524,7.9912142,10.2087560,13.0489301,10.2092634,11.4029668,10.3103281,10.2810316,8.9487624,14.2699307,12.8538251,10.7545354,18.0638133,7.2115769,7.4020585,7.9737234,13.1687588,13.7186238,9.6881618,4.2991770,11.4829896,8.0113006,10.0285544,8.3325591,8.8476239,9.3618137,11.0913308,10.2702207,12.0215701,11.8083744,8.1575837,10.0413629,11.7291752,13.8315537,12.4823312,13.3289096,8.5874403,9.8624401,7.0444818,13.9701389,10.0250634,14.3841966,17.4074390,13.1290358,8.3764673,7.8796107,6.4597773,12.4989708,11.3617236,5.0730931,13.5990536,9.4800716,11.1247161,12.6283343,12.5711367,10.8075848,13.2183856,12.4566869,17.0046899,9.9132293,13.8912393,10.4806343,6.7550983,18.4982020,4.6835563,4.6068688,8.4304188,7.8747286,9.4440702,12.1033704,10.7397568,12.4483258,12.0952273,9.4609549,16.1755646,13.2110564,12.5244792,14.5511670,14.9365263,6.6852081,14.6988321,9.8833093,11.1549852,14.4090081,6.2565184,8.3488705,10.8509966,7.6795679,13.5814813,10.1733942,12.1773482,4.7032686,9.9248308,17.7067155,8.2378404,12.8208154,12.7675305,9.0907063,9.5720411,4.5536981,5.2252539,10.7393508,8.1761239,7.8011878,10.8517959,12.8793471,10.1738281,9.0522516,9.7020267,8.5743543,7.1063673,9.4366173,7.5154902,9.2420952,13.7275687,8.2097051,12.4686117,8.6426135,10.6854081,14.8617929,14.2631291,11.1449327,8.4807248,5.9399190,6.7772300,7.2566033,10.3215210,9.2483564,10.8592844,13.8227188,5.8955118,6.8936159,11.4641992,8.6535466,14.1301887,10.2194653,9.3929177,11.8592296,9.3153675,10.8574024,9.5293558,14.1394531,7.1224090,5.6785198,13.1351723,7.1031658,7.6344684,8.6918016,6.8426780,8.6902514,9.9025967,6.1603559,6.3995948,6.7157089,14.9359341,13.1275476,11.2493476,10.7684760,8.5263731,5.1711855,10.2432689,6.7908688,9.2634794,5.6242460,7.7319788,13.7579540,10.5344149,11.2123002,9.5503450,11.3042249,6.6581916,13.0363709,9.0141363,6.8815546,8.6309000,9.4825677,6.9816465,9.4836443,8.5629547,12.5643187,13.2918150,4.9542483,3.8941388,12.0723769,14.6818075,6.2067566,8.6538934,11.4860264,9.6481396,12.7096758,7.8361298,12.0167492,9.2011051,6.7472607,13.5725275,15.0862343,12.5248807,10.8804527,12.7291198,7.7527975,7.8537703,10.5257599,11.2615216,5.2586963,9.3935784,4.8959811,14.9649019,9.7550081,9.0961317,3.0822901,10.4690830,11.4116176,11.8268286,9.6303294,12.6595176,10.3003485,10.6738841,7.1545388,13.1700952,8.8394611,11.7666496,5.3739818,12.5156287,10.5998309,7.9280247,11.3985509,9.3435626,9.1445783,7.5190392,10.5207065,5.5194295,14.4021779,7.9815022,7.3148241,5.0131517,12.1867856,3.4892615,14.7278153,10.0177503,9.0080577,6.2549383,11.5792232,10.0743671,4.6603495,9.1943305,10.0549778,13.3946923,11.0435648,11.9903902,7.5212459,6.9752799,9.7793759,3.0074422,9.9630136,8.2949444,14.4448033,8.8767257,10.4919437,12.8309614,11.9987884,9.4450733,7.1909711,7.7836130,12.0111407,7.8110426,8.8857522,7.2070115,6.1091037,15.5397454,12.4138856,11.0948175,10.3384724,4.0731303,11.9523302,11.7543732,8.6845056,11.3963952,9.1248950,9.8663549,14.4536098,10.5610537,9.6523570,9.9533877,10.1019772,12.0909679,12.1466894,9.8986813,14.2406526,10.1251599,13.5607593,8.3409267,7.3538062,9.2187909,8.3878572,9.6934979,6.8270478,6.9754722,14.7438670,6.2118150,4.3408116,11.4874280,12.9580969,9.5487183,10.2743684,11.2433385,14.4445854,10.3395096,5.7534609,10.5550234,10.9322053,10.2105928,11.3020951,12.9484069,6.5904212,8.4368601,11.3280691,8.6031823,7.6938566,11.3733151,12.3900593,11.7711757,11.2307516,13.4915701,10.7228153,7.3886924,8.4401787,10.2753493,8.4389663,12.1972728,10.4918743,10.6289742,10.5594228,6.7236908,11.2358099,8.5938861,12.3906280,14.4511787,7.4746119,15.8803774,2.5522927,9.6801286,8.5697501,10.8271935,13.5280438,10.6818935,13.5646711,3.5187030,10.4440143,9.8327296,9.7382627,14.1669606,6.9083257,3.8266181,13.6244062,11.0284378,9.5523319,8.9891586,9.9055215,8.3856238,8.7478998,6.6987620,14.7248918,9.2529918,10.2082195,4.9534370,9.2030317,5.2269606,8.0661516,13.1779369,5.2971835,15.0037013,7.2702621,6.9997505,9.6490126,13.9149660,10.7425870,9.7558964,12.5752855,10.5098261,20.2689637,9.8681830,7.8259004,9.4911900,9.6024895,7.6085691,12.0086596,6.6780724,8.2764670,8.9880572,15.9231426,5.9905542,13.5816388,8.9839322,9.5235545,10.1314783,13.1174616,8.1648447,12.5653484,12.4941364,10.5916275,12.7761500,9.8608664,8.1374522,10.6055768,6.5465219,11.7945966,7.0397647,4.4046833,12.4284773,0.4180241,12.0268339,10.0441325,5.3276329,8.4208769,8.5484829,9.8222639,9.4951750,9.3263556,13.7433301,10.1112279,12.3558939,10.8694158,9.7864777,5.5161601,7.0906274,14.5786803,12.9236138,8.9206195,7.0104273,5.8283839,7.6944516,6.2924265,10.0766522,10.3576597,8.5793193,11.2022858,4.9360148,6.5907700,13.0853471,9.5498965,10.8132248,7.3545704,9.3583861,10.5726301,6.8032692,9.5914570,6.1383186,7.0176580,16.8026498,6.7959168,9.2745414,7.7390857,12.5977623,8.6116698,13.6735060,10.8476068,9.6710713,10.1086791,9.6101003,11.2849373,14.3841286,10.0175111,5.9766042,9.2654916,12.3336237,11.0695365,9.4801954,6.6405542,11.7110714,9.2962742,4.5557592,7.9725970,10.3105591,9.1068024,8.1585631,14.9021906,9.2015137,15.0472571,9.1225965,13.9551835,15.1033478,10.6360240,12.0867865,15.6969704,9.5818060,8.1641150,8.2950194,8.6544478,7.9130456,8.8904450,13.9381998,8.9913977,14.0155779,6.2856039,10.7923301,8.8070441,11.2657258,10.7901363,9.1724396,6.6433443,9.5172255,12.3402514,2.7254577,12.4006210,13.2697124,10.0670987,15.3858112,8.2044828,10.7534955,7.9282064,10.9170642,12.8222748,18.2680638,9.0601854,13.2616197,7.0193571,12.2447467,5.3729936,14.8064727,10.5359554,10.4851627,11.8312380,13.3435483,10.5894537,5.0047413,7.5532502,11.9171854,12.1777692,7.6730359,5.5515027,12.3027227,10.1575062,14.8505769,9.6526219,11.2016182,10.7898901,13.6303578,12.8561220,13.3002161,9.0945849,4.9117132,8.0514791,8.3684288,4.7461608,6.3118847,14.3888758,15.8801467,11.6563489,7.9043481,6.1992280,10.4055679,6.4948166,11.8656277,3.8399970,9.5901581,8.6379262,7.4541442,7.1135626,7.9164363,9.6439593,15.6259631,7.3244170,8.4635798,12.0317526,17.1847365,12.5357554,6.0369018,12.9830581,11.2712555,12.3488084,9.3935706,8.1248854,11.4523131,9.6710694,9.5978474,15.1563587,7.5582530,10.8587757,13.5890062,10.1390991,8.1443215,16.1032757,6.5988579,9.6915113,7.6946942,10.5688193,7.9222074,6.0964578,7.0383112,11.5956154,6.6059072,13.5679685,15.1021379,10.2625096,10.2202339,15.7814051,16.3342713,6.1339245,0.9275113,15.8169582,11.0888355,7.8822788,15.2039942,9.6944328,11.7292036,11.6230714,8.4657438,7.6462181,7.1888162,8.1788400,13.7221572,12.4793501,10.4488461,8.9233659,8.9305724,7.4913262,12.5882791,10.6825315,10.8527571,12.1660301,12.4390247,13.8529219,8.5372836,11.2575812,6.4922496,9.5404721,10.7082122,11.2365487,10.2713802,14.8685632,10.7735798,10.6526134,4.8455022,8.3135583,10.8120056,7.2903999,7.0497880,4.9958942,5.9730174,9.8642732,11.5609671,10.1178216,6.6279774,9.2441754,9.9419299,13.4710469,6.0601435,8.2095239,7.9456672,12.7039825,7.4197810,9.5928275,8.2267352,2.8314614,11.5653497,6.0828073,11.3926117,10.5403929,14.9751607,11.7647580,8.2867261,10.0291522,7.7132033,6.3337642,14.6066222,11.3436587,11.2717791,10.8818323,8.0320657,6.7354041,9.1871676,13.4381778,7.4353197,8.9210043,10.2010750,11.9442048,11.0081195,4.3369520,13.2562675,15.9945674,8.7528248,14.4948086,14.3577443,6.7438382,9.1434984,15.4599419,13.1424011,7.0481925,7.4823108,10.5743730,6.4166006,11.8225244,8.9388744,10.3698150,10.3965596,13.5226492,16.0069239,6.1139247,11.0838351,9.1659242,7.9896031,10.7282936,14.2666492,13.6478802,10.6248561,15.3834373,11.5096033,14.5806570,10.7648690,5.3407430,7.7535042,7.1942866,9.8867927,12.7413156,10.8127809,8.1726772,8.3965665)

.. is there some easy way in R to programmatically and automatically find the most likely distribution and the estimated distribution parameters?

Please note that the distribution identification code will be part of an automated process, so manual intervention in the identification won't be possible.

Answer 1

My first approach would be to generate qq plots of the given data against the possible distributions.

x <- c(15.771062,14.741310,9.081269,11.276436,11.534672,17.980860,13.550017,13.853336,11.262280,11.049087,14.752701,4.481159,11.680758,11.451909,10.001488,11.106817,7.999088,10.591574,8.141551,12.401899,11.215275,13.358770,8.388508,11.875838,3.137448,8.675275,17.381322,12.362328,10.987731,7.600881,14.360674,5.443649,16.024247,11.247233,9.549301,9.709091,13.642511,10.892652,11.760685,11.717966,11.373979,10.543105,10.230631,9.918293,10.565087,8.891209,10.021141,9.152660,10.384917,8.739189,5.554605,8.575793,12.016232,10.862214,4.938752,14.046626,5.279255,11.907347,8.621476,7.933702,10.799049,8.567466,9.914821,7.483575,11.098477,8.033768,10.954300,8.031797,14.288100,9.813787,5.883826,7.829455,9.462013,9.176897,10.153627,4.922607,6.818439,9.480758,8.166601,12.017158,13.279630,14.464876,13.319124,12.331335,3.194438,9.866487,11.337083,8.958164,8.241395,4.289313,5.508243,4.737891,7.577698,9.626720,16.558392,10.309173,11.740863,8.761573,7.099866,10.032640) > qqnorm(x) 

For more info see link

Another possibility is based on the fitdistr function in the MASS package. Here is the different distributions ordered by their log-likelihood

> library(MASS) > fitdistr(x, 't')$loglik [1] -252.2659 Warning message: In log(s) : NaNs produced > fitdistr(x, 'normal')$loglik [1] -252.2968 > fitdistr(x, 'logistic')$loglik [1] -252.2996 > fitdistr(x, 'weibull')$loglik [1] -252.3507 > fitdistr(x, 'gamma')$loglik [1] -255.9099 > fitdistr(x, 'lognormal')$loglik [1] -260.6328 > fitdistr(x, 'exponential')$loglik [1] -331.8191 Warning messages: 1: In dgamma(x, shape, scale, log) : NaNs produced 2: In dgamma(x, shape, scale, log) : NaNs produced 

Answer 2

Another similar approach is using the fitdistrplus package

library(fitdistrplus) 

Loop through the distributions of interest and generate 'fitdist' objects. Use either "mle" for maximum likelihood estimation or "mme" for matching moment estimation, as the fitting method.

f1<-fitdist(x,"norm",method="mle") 

Use bootstrap re-sampling in order to simulate uncertainty in the parameters of the selected model

b_best<-bootdist(f_best) print(f_best) plot(f_best) summary(f_best) 

The fitdist method allows for using custom distributions or distributions from other packages, provided that the corresponding density function dname, the corresponding distribution function pname and the corresponding quantile function qname have been defined (or even just the density function).

So if you wanted to test the log-likelihood for the inverse normal distribution:

library(ig) fitdist(x,"igt",method="mle",start=list(mu=mean(x),lambda=1))$loglik 

You may also find Fitting distributions with R helpful.

Answer 3

(Answer edited to add additional explanation)

1. You can't really find "the" distribution; the actual distribution from which data are drawn can nearly always* be guaranteed not to be in any "laundry list" provided by any such software. At best you can find "a" distribution (more likely several), one that is an adequate description. Even if you find a great fit there are always an infinity of distributions that are arbitrarily close by. Real data tends to be drawn from heterogeneous mixtures of distributions that themselves don't necessarily have simple functional form.

   * an example where you might hope to is where you know the data were actually generated from exactly one distribution on a list, but such situations are extremely rare.

2. I don't think just comparing likelihoods is necessarily going to make sense, since some distributions have more parameters than others. AIC might make more sense, except that ...

3. Attempting to identify a "best fitting" distribution from a list of candidates will tend to produce overfitting, and unless the effect of such model selection is accounted for properly will lead to overconfidence (a model that looks great but doesn't actually fit the data not in your sample). There are such possibilities in R (the package fitdistrplus comes to mind), but as a common practice I would advise against the idea. If you must do it, use holdout samples or cross-validation to obtain models with better generalization error.

Answer 4

I find it hard to imagine a realistic situation where this would be useful. Why not use a non-parametric tool like a kernel density estimate?