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Update model comparison and SMC notebooks #2855

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Merged
merged 2 commits into from
Feb 14, 2018

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aloctavodia
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Update notebooks following guidelines in #2834, also fix some typos and update deprecated syntax.

@junpenglao
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LGTM.

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@gBokiau gBokiau left a comment

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(nitpicking really)

@@ -114,20 +73,20 @@
" \n",
" NOTE: latent_sigma_y is used to create a normally distributed,\n",
" 'latent error' aka 'inherent noise' in the 'physical process' \n",
" generating thses values, rather than experimental measurement error. \n",
" generating theses values, rather than experimental measurement error. \n",
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these--s--

…in the ‘physical' data generating process, rather…

would sound more familiar IMO

"metadata": {},
"source": [
"Back to the real purpose of this Notebook: demonstrate model selection.\n",
"Back to the real purpose of this Notebook, demonstrate model selection.\n",
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, to demonstrate

@@ -1133,8 +1010,7 @@
"\n",
"+ Quadratic-generated data (rhs):\n",
" + The WAIC is also quite flat across the models\n",
" + The lowest WAIC is model **k4**, but **k3** - **k5** are more or less the same. \n",
" "
" + The lowest WAIC is model **k4**, but **k3** - **k5** are more or less the same. "
]
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Looking at the plots, I believe this should be k3 - k4

@@ -1224,7 +1093,23 @@
"\n",
"It is important to keep in mind that, with more data points, the real underlying model (one that we used to generate the data) should outperforms other models. \n",
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should outperform--s--

@@ -1224,7 +1093,23 @@
"\n",
"It is important to keep in mind that, with more data points, the real underlying model (one that we used to generate the data) should outperforms other models. \n",
"\n",
"In general, PSIS-LOO is recommended. To quote from [avehtari's comment](https://github.com/pymc-devs/pymc3/issues/938#issuecomment-313425552): \"I also recommend using PSIS-LOO instead of WAIC, because it's more reliable and has better diagnostics as discussed in http://link.springer.com/article/10.1007/s11222-016-9696-4 (preprint https://arxiv.org/abs/1507.04544), but if you insist to have one information criterion then leave WAIC\". Alternatively Watanabe [says](http://watanabe-www.math.dis.titech.ac.jp/users/swatanab/index.html) \"WAIC is a better approximator of the generalization error than the pareto smoothing importance sampling cross validation. The Pareto smoothing cross validation may be the better approximator of the cross validation than WAIC, however, it is not of the generalization error\"."
"In general, PSIS-LOO is recommended. To quote from [avehtari's comment](https://github.com/pymc-devs/pymc3/issues/938#issuecomment-313425552): \"I also recommend using PSIS-LOO instead of WAIC, because it's more reliable and has better diagnostics as discussed in http://link.springer.com/article/10.1007/s11222-016-9696-4 (preprint https://arxiv.org/abs/1507.04544), but if you insist to have one information criterion then leave WAIC\". Alternatively, Watanabe [says](http://watanabe-www.math.dis.titech.ac.jp/users/swatanab/index.html) \"WAIC is a better approximator of the generalization error than the pareto smoothing importance sampling cross validation. The Pareto smoothing cross validation may be the better approximator of the cross validation than WAIC, however, it is not of the generalization error\"."
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There is some agreement that PSIS-LOO offers the best indication of a model's quality.

"metadata": {},
"source": [
"##### Now loop through all the models and calculate the WAIC"
"In this case we are interested in the WAIC score, we can plot also the standard error of the estimation, which is nice.\n",
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In this case we are interested in the WAIC score. We also plot error bars for the standard error of the estimated scores. This gives us a more accurate view of how much they might differ.

@aloctavodia
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thanks @gBokiau for your help. I included almost all your suggestions.

@junpenglao junpenglao merged commit 0446166 into pymc-devs:master Feb 14, 2018
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3 participants