
---
title: "Example 2: Penguin dataset with torch and luz"
output: 
  rmarkdown::html_vignette:
    toc: true
always_allow_html: yes
vignette: >
  %\VignetteIndexEntry{Example 2: Penguin dataset with torch and luz}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
  &\VignetteDepends{luz, palmerpenguins, GGally}
---

```{r, include = FALSE}
knitr::opts_chunk$set(
  fig.dpi = ifelse(Sys.getenv("RENDER_PLOTLY", unset = 0) == 1, 400, 50),
  collapse = TRUE,
  comment = "#>",
  fig.align = "center",
  out.width = "90%",
  eval = requireNamespace("palmerpenguins") & requireNamespace("luz") &
    torch::torch_is_installed()
)
```

```{r, echo = FALSE}
Sys.setenv(LANG = "en_US.UTF-8")
set.seed(111)
torch::torch_manual_seed(111)
```


> **`r knitr::asis_output("\U1F4DD")`  Note**  
> Since the **innsight** package relies on the **torch** package for each 
method and requires a successful installation of LibTorch and other 
dependencies (`torch::install_torch()`), no examples can be run in the R 
vignette for memory reasons. For the executed code chunks, we refer to [our website](https://bips-hb.github.io/innsight/articles/Example_2_penguin.html).


This example is even slightly more complex than the [first
one](https://bips-hb.github.io/innsight/articles/Example_1_iris.html),
considering the Iris dataset, because we are using the [penguin
dataset](https://allisonhorst.github.io/palmerpenguins/), which has both numeric
and categorical variables. Since our package **innsight** currently only accepts
numeric values as inputs, you have to keep a few points in mind and use little
tricks. But in the future, it should be possible to use categorical variables
directly with the package. In addition, we want to show how to use **torch**
models trained with the higher level API
[**luz**](https://mlverse.github.io/luz/) in this example.

## Explore the dataset

The dataset includes measurements of penguin species Adelie ($162$), Chinstrap
($68$), and Gentoo ($124$) collected near Palmer Station, Antarctica. For each
of the $344$ penguins, numerical values of bill length/depth, flipper length,
body mass, and study year were measured, and additional categorical
characteristics like sex and island were recorded. To give you a brief overview
of the data, let's create a pair plot of some variables using
**GGally**:

```{r, warning=FALSE, fig.width=12, fig.height=8, message=FALSE}
library(palmerpenguins)

# remove NAs
penguin_data <- na.omit(penguins)
# create plot
GGally::ggpairs(penguin_data,
  ggplot2::aes(color = species, alpha = 0.75),
  columns = 3:7,
  progress = FALSE
)
```

Based on this graphic, we can already hypothesize which 
characteristics might be relevant for the individual classes. For example, 
it is visible that the Gentoo species (blue) is much heavier, has longer 
flippers and thinner bills than the other species. On the other hand, for the 
species Adelie (red), the bill length could be a decisive feature for the 
classification. In the following, we will see if these hypotheses match 
the results of the feature attribution methods.

## Step 0: Train a model

The package **luz** makes things much easier for training a **torch** model,
e.g., by doing the for-loop over the epochs for you. However, the model must be
defined as [`nn_module`](https://torch.mlverse.org/docs/reference/nn_module.html) 
and the data as a [`torch::dataset`](https://torch.mlverse.org/docs/reference/dataset.html), 
but currently, **innsight** only works with **torch** models of class [`nn_sequential`](https://torch.mlverse.org/docs/reference/nn_sequential.html). 
Therefore a data preparation step and a few tricks are necessary to use 
sequential models trained in **luz** with the package **innsight**.

### Data preparation

As previously mentioned, **innsight** needs numeric input, and **luz** needs a 
**torch** dataset. For this reason, we create a dataset with already encoded 
categorical variables (for more information about the `dataset` defined for
**torch** models see the 
[**torch** vignette](https://torch.mlverse.org/start/custom_dataset/)).


```{r setup, fig.width=16}
# Load packages
library(torch)
library(luz)


# Create torch penguin dataset
penguin_dataset <- dataset(
  name = "penguin_dataset",
  initialize = function(df) {
    df <- na.omit(df) # remove NAs

    # Get all numeric features and transform them to `torch_tensor`
    x_cont <- df[, c(
      "bill_length_mm", "bill_depth_mm", "flipper_length_mm",
      "body_mass_g", "year"
    )]
    x_cont <- torch_tensor(as.matrix(x_cont))

    # Get and encode (one-hot) categorical features and transform them to `torch_tensor`
    x_cat <- sapply(df[, c("island", "sex")], as.integer)
    x_cat <- torch_tensor(x_cat, dtype = torch_int64())
    x_cat <- torch_hstack(list(
      nnf_one_hot(x_cat[, 1]),
      nnf_one_hot(x_cat[, 2])
    ))

    # Stack and store all features together in the field 'x'
    self$x <- torch_hstack(list(x_cont, x_cat))

    # Get, transform and store the target variable (the three penguin species)
    self$y <- torch_tensor(as.integer(df$species))
  },
  .getitem = function(i) {
    list(x = self$x[i, ], y = self$y[i])
  },
  .length = function() {
    self$y$size()[[1]]
  }
)
```

Using the above method, we can now create a **torch** dataset from any subset of 
instances from the penguin dataset. Consequently, we can now get a training 
and validation dataset and build a data loader provided by the function 
[`torch::dataloader`](https://torch.mlverse.org/docs/reference/dataloader.html).
Beforehand, however, we normalize all numerical inputs:

```{r}
# Normalize inputs
scaled_penguin_ds <- penguin_data
scaled_penguin_ds[, c(3:6, 8)] <- scale(penguin_data[, c(3:6, 8)])

# Create train and validation split
idx <- sample(seq_len(nrow(penguin_data)))
train_idx <- idx[1:250]
valid_idx <- idx[251:333]

# Create train and validation datasets
train_ds <- penguin_dataset(scaled_penguin_ds[train_idx, ])
valid_ds <- penguin_dataset(scaled_penguin_ds[valid_idx, ])

# Create dataloaders
train_dl <- dataloader(train_ds, batch_size = 32, shuffle = TRUE)
valid_dl <- dataloader(valid_ds, batch_size = 32, shuffle = FALSE)

# We use the whole dataset as the test data
test_ds <- penguin_dataset(scaled_penguin_ds)
```

### Create and train the model

The package **luz** requires an object of the class `nn_module`, which cannot be
used for **innsight**. But a sequential model can be nested in a `nn_module` and
extracted afterward. For this reason, we define a model that uses only the
sequential network of class `nn_sequential` stored as a field. In the same way,
you can assemble a model from several sequential models and, if necessary, apply
each model individually with **innsight**. For example, if you want to use several
data pre-processing layers before the actual model.

```{r}
# Create the model
net <- nn_module(
  initialize = function(dim_in) {
    # Here, we define our sequential model
    self$seq_model <- nn_sequential(
      nn_linear(dim_in, 256),
      nn_relu(),
      nn_dropout(p = 0.4),
      nn_linear(256, 256),
      nn_relu(),
      nn_dropout(p = 0.4),
      nn_linear(256, 64),
      nn_relu(),
      nn_dropout(p = 0.4),
      nn_linear(64, 3),
      nn_softmax(dim = 2)
    )
  },

  # The forward pass should only contain the call of the sequential model
  forward = function(x) {
    self$seq_model(x)
  }
)
```

Now we can easily train the model with **luz** and extract the sequential model
to be used for **innsight**:

```{r}
# We have imbalanced classes, so we weight the output classes accordingly
weight <- length(train_ds$y) /
  (3 * torch_stack(lapply(1:3, function(i) sum(train_ds$y == i))))

# Fit the model
fitted <- net %>%
  setup(
    loss =
      function(input, target) nnf_nll_loss(log(input), target, weight = weight),
    optimizer = optim_adam,
    metrics = list(
      luz_metric_accuracy()
    )
  ) %>%
  set_hparams(dim_in = 10) %>%
  fit(train_dl, epochs = 50, valid_data = valid_dl)

# Extract the sequential model
model <- fitted$model$seq_model

# Show result
get_metrics(fitted)[c(99, 100, 199, 200), ]
```

## Step 1: Convert the model

Analogous to the [first
example](https://bips-hb.github.io/innsight/articles/Example_1_iris.html)
considering the Iris dataset, we can easily create the `Converter` object by
passing the extracted model and the input dimension to the R6 class. However,
since the categorical variables have already been encoded, there are a total of
$10$ inputs ($5$ numeric features, $3$ islands and $2$ genders) and the input
names (optional argument) must be expanded accordingly.

```{r}
library(innsight)

# Define input and output names
input_names <-
  c(
    "bill_length", "bill_depth", "flipper_length", "body_mass", "year",
    "island_Biscoe", "island_Dream", "island_Torgersen",
    "sex_female", "sex_male"
  )
output_names <- c("Adelie", "Chinstrap", "Gentoo")

# Create the `Converter` object
converter_1 <- Converter$new(model,
  input_dim = 10,
  input_names = input_names,
  output_names = output_names
)
```

But it is also possible, with the help of a small hack, to combine the results
of the categorical variables, for example, to get only one relevance value for 
the overall feature island and not for each of the three islands. This will be 
explained in the next step and we create a converter for this variant here:

```{r}
# Create a second `Converter` object for combined categorical features
converter_2 <- Converter$new(model,
  input_dim = 10,
  output_names = output_names
)
```

## Step 2: Apply methods

Now we can apply the implemented methods to our trained model. Although these
methods are different, they are called more or less the same way in
**innsight**. Essential arguments are, of course, the converter object
(`converter`) and the data (`data`) to which the method is to be applied. There
are also other basic and model-specific arguments, but they are already
explained in the other more [detailed
vignette](https://bips-hb.github.io/innsight/articles/detailed_overview.html#step-2-apply-selected-method).
Now two possibilities are presented with the categorical variables: either
considering the categorical expressions individually or summarizing them.

### Separated categorical variables

In this variant, nothing needs to be changed, because it already corresponds 
to the default result, i.e., you can use the method of your choice as usual:

```{r}
# Data to be analyzed (in this case, we use the whole dataset)
data <- test_ds$x
# Apply method 'LRP' with rule alpha-beta
lrp_ab_1 <- LRP$new(converter_1, data, rule_name = "alpha_beta", rule_param = 2)

# the result for 333 instances, 10 inputs and all 3 outputs
dim(get_result(lrp_ab_1))
```

### Summarized categorical variables

In this case, we need to use a few tricks to make it clear to the method 
object that instead of $10$ inputs, there are only $7$ ($5$ numeric and $2$ 
categorical). On the one hand, the input dimension and the input names have 
to be adjusted in the passed converter object; On the other hand, the results 
of the categorical features have to be combined so that the field 
`result` fits the input dimensions again:

```{r, results='hide', message=FALSE}
# Apply method as in the other case
lrp_ab_2 <- LRP$new(converter_2, data, rule_name = "alpha_beta", rule_param = 2)

# Adjust input dimension and input names in the method converter object
lrp_ab_2$converter$input_dim[[1]] <- 7
lrp_ab_2$converter$input_names[[1]][[1]] <-
  c(
    "bill_length", "bill_depth", "flipper_length", "body_mass", "year",
    "island", "sex"
  )

# Combine (sum) the results for feature 'island' and 'sex'
lrp_ab_2$result[[1]][[1]] <- torch_cat(list(
  lrp_ab_2$result[[1]][[1]][, 1:5, ], # results for all numeric features
  lrp_ab_2$result[[1]][[1]][, 6:8, ]$sum(2, keepdim = TRUE), # results for feature island
  lrp_ab_2$result[[1]][[1]][, 9:10, ]$sum(2, keepdim = TRUE) # results for feature sex
),
dim = 2
)

# Now we have the desired output shape with combined categorical features
dim(get_result(lrp_ab_2))
#> [1] 333  7  3
```

> **`r knitr::asis_output("\U1F4DD")`  Note**  
> Even if the input names can be passed to the converter in other ways, 
they will be stored internally as a list (input layer) of lists (for each 
dimension). Since, in this case, we have only one input layer and only one 
feature dimension, it is sufficient to modify only 
`lrp_ab_2$converter$input_names[[1]][[1]]`. In the same way, regardless of 
the model's architecture, the result is stored as a list (output layer) 
of lists (input layer), which is why in our case two lists are indexed by `1` 
before the results are modified.

## Step 3: Visualization

The package **innsight** provides two ways to visualize the results of a method,
namely as `innsight_ggplot2` or `innsight_plotly` object. Both are S4 classes to
combine multiple plots nicely and to be able to make visual modifications or
adjustments to the selection of plots even after the object has been created.
The first class is based on [**ggplot2**](https://ggplot2.tidyverse.org/) and
behaves partly like an ordinary **ggplot2** object. Whereas the other one is
based on the [**plotly**](https://plotly.com/r/) package and creates an
interactive graph with more detailed information about each variable. For more
information on the S4 classes `innsight_ggplot` and `innsight_plotly` see the
[in-depth
vignette](https://bips-hb.github.io/innsight/articles/detailed_overview.html#advanced-plotting)
or the respective R documentation (`?innsight_ggplot2` or `?innsight_plotly`).

For each of these classes and thus, of course, also for each method, there are
two plot functions:  

* `plot()` shows only individual data points and
* `boxplot()` visualizes summaries of multiple data points using summary statistics.

### Plot individual results

The function `plot()` is implemented for each of the available methods. You can 
select your desired data points and output nodes/classes with the `data_idx` 
and `output_idx` arguments, respectively. To switch between a **ggplot2** and 
**plotly** based plot, you can use the logical `as_plotly` argument, but 
this requires a successful installation of the suggested **plotly** package.

Now we plot the results for the first instance and the classes Adelie and 
Gentoo (output indices $1$ and $3$), but once with separated and once with 
merged categorical variables:

```{r, fig.width=8}
library(ggplot2)
# Separated categorical features
plot(lrp_ab_1, output_idx = c(1, 3)) +
  coord_flip()
# Combined categorical features
plot(lrp_ab_2, output_idx = c(1, 3)) +
  coord_flip()
```

  
**Interpretation**

In this case, we analyze the first data point of the test data `test_ds`, 
which is also the first instance in the penguin dataset `penguin_data`.
Unnormalized, it looks like this:

```{r, echo = FALSE}
knitr::kable(penguin_data[1, ])
```

This is an Adelie penguin, and it exactly shows what we thought at the 
beginning of this example: The key feature that argues for the class Adelie 
is the bill length (`bill_length_mm`). As you can see in the figures above, 
it has by far the highest positive relevance for the class Adelie and a very 
high negative relevance for the class Gentoo. In other words, the comparatively 
short bill length strongly argues for the class Adelie and, on the other hand, 
prevents the instance from being the species Gentoo. 

Of course, you can also investigate the other features more deeply, such as 
the island (`island`) on which the penguin was spotted. The Gentoo penguins were only 
sighted on Biscoe Island and Chinstrap penguins only on Dream, whereas the 
Adelie penguins were equally sighted on all three islands. For this reason, 
it makes sense that for our example penguin sighted on Torgersen Island, a
positive relevance for the species Adelie and a negative relevance for Gentoo 
resulted.

### Plot summarized results

The function `boxplot()` is implemented for each of the available local methods. 
You can select your desired data points (default is `'all'`) and output 
nodes/classes with the `data_idx` and `output_idx` arguments, respectively. 
To switch between a **ggplot2** and **plotly** based plot, you can use the 
logical `as_plotly` argument, but this requires a successful installation of 
the suggested **plotly** package. In addition, you can use `ref_data_idx` to 
select a single data point that will be visualized in red as a reference 
value, and `preprocess_FUN` to select a function that will be applied to all 
relevances in advance (e.g., the absolute value).

```{r, fig.width=8}
library(ggplot2)

boxplot(lrp_ab_2,
  output_idx = c(1, 3), preprocess_FUN = identity,
  ref_data_idx = 1
) +
  coord_flip() +
  facet_grid(rows = vars(output_node))
```

**Interpretation**

This global result also reflects the ideas from the introduction: The feature 
`bill_length` seems to have a very strong positive influence on the species 
Adelie and a negative one on the class Gentoo. On the other hand, the variables 
of the penguin's body weight (`body_mass`), flipper length (`flipper_length`) 
and bill depth (`bill_depth`) have mostly a positive relevance on the class 
Gentoo.
