MLCA Week 10:

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# MLCA Week 10:
## Followup
### Mike Mahoney
### 2021-11-02

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# Project FAQ

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### Cross-entropy (from week 7 - tuning RF):

```r
calc_cross_entropy <- function(rf_model, data) {
  data <- predict(rf_model, data) |> 
  predictions() |> 
  cbind(data) |> 
  mutate(prediction = ifelse(Attrition == "Yes", Yes, No),
         # Force prediction to not be exactly 0 or 1
         prediction = max(1e-15, min(1 - 1e-15, prediction)),
         loss = -log(prediction))
  sum(-log(data$prediction))
}
```

### Cross-entropy: negative log of the probability of _the correct classification_

### `ranger`: provides predictions of both classes

### `lightgbm`: provides predictions of _the positive class_

---

### So alteration needed:

```r
calc_cross_entropy <- function(lgb_model, data) {
  data <- data |>
    mutate(predict(lgb_model, data),
           # If the correct answer is No, invert the prediction:
           prediction = ifelse(Attrition == "Yes", 
                               prediction, 
                               1 - prediction),
         # Force prediction to not be exactly 0 or 1
         prediction = max(1e-15, min(1 - 1e-15, prediction)),
         loss = -log(prediction))
  sum(-log(data$prediction))
}
```

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### Just because it _worked_ doesn't mean it's _working_

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## Standard citations:

```r
citation()
```

```
## 
## To cite R in publications use:
## 
##   R Core Team (2021). R: A language and environment for statistical
##   computing. R Foundation for Statistical Computing, Vienna, Austria.
##   URL https://www.R-project.org/.
## 
## A BibTeX entry for LaTeX users is
## 
##   @Manual{,
##     title = {R: A Language and Environment for Statistical Computing},
##     author = {{R Core Team}},
##     organization = {R Foundation for Statistical Computing},
##     address = {Vienna, Austria},
##     year = {2021},
##     url = {https://www.R-project.org/},
##   }
## 
## We have invested a lot of time and effort in creating R, please cite it
## when using it for data analysis. See also 'citation("pkgname")' for
## citing R packages.
```

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## Other standard cites

```r
citation("ranger") # RF
citation("lightgbm") # GBM
citation("kernlab") # SVM
citation("caret") # KNN
citation("rpart") # Decision trees
```

Breiman, L., 2001. Random Forests. Machine Learning 45, 5–32. https://doi.org/10.1023/A:1010933404324

Friedman, J. H., 2002. Stochastic Gradient Boosting. Computational Statistics & Data Analysis 38(4), 367-378. https://doi.org/10.1016/S0167-9473(01)00065-2

Cortes, C., Vapnik, V. Support-vector networks. Machine Learning 20, 273–297 (1995). https://doi.org/10.1007/BF00994018

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# Other notes:

### Don't force-install packages (it's rude)

### Don't cite LM, GLM

### Pay attention to the rubric (if it isn't there, it isn't worth points)

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# Project re-submit

### Optional!

### I make no promises about turnaround time (but measured in days, not hours.)

### No resubmission after 2021-12-08.

### First project has been finished!

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# Status Update

### One more week of content (SVM)

### Three "work weeks" (bring questions)

### Presentations 2021-12-08