{maize} package

maize

what is {maize}?

{maize} is an extension library for kernels & support vector machines in tidymodels! The package consists of additional kernel bindings that are not available in the {parsnip} or {recipes} package. Many of the kernels are ported from {kernlab}, additional kernels have been added directly to maize transposed from Python and Julia packages.

{parnsip} has three kernels available: linear, radial basis function, & polynomial. {maize} extends to further kernels, other engines, and adds steps for {recipes}:

maize engines

Example Overview

corn kernels and svm kernels

say we have three types of corn with different size kernels which create different height corn. we could (1) create a support vector machine that can predict the height of the corn given the kernel type and kernel size, we could also (2) predict the corn type given the kernel size and corn height.

corn kernel dataset

library(parsnip)
library(maize)
library(ggplot2)


# use this later to create a classification field
# -----------------------------------------------
kernel_min <- corn_data$kernel_size |> min()
kernel_max <- corn_data$kernel_size |> max()
kernel_vec <- seq(kernel_min, kernel_max, by = 1)
height_min <- corn_data$height |> min()
height_max <- corn_data$height |> max() 
height_vec <- seq(height_min, height_max, by = 1)
corn_grid <- expand.grid(kernel_size = kernel_vec, height = height_vec)
# -----------------------------------------------

maize::corn_data |>
    ggplot() +
    geom_point(aes(x = kernel_size, y = height, color = type)) +
    theme_minimal() +
    labs(title = 'corn kernel data') 

Regression

regression for corn kernel height given a specialty svm kernel

set.seed(31415)
corn_train <- corn_data |> dplyr::sample_frac(.80)
corn_test  <- corn_data |> dplyr::anti_join(corn_train)

Joining with `by = join_by(height, kernel_size, type)`

# model params --
  svm_reg_spec <- 
    svm_bessel(cost = 1, margin = 0.1) |> 
    set_mode("regression") |>
    set_engine("kernlab")


# fit --

  svm_reg_fit <- svm_reg_spec |> fit(height ~ ., data = corn_train)

 Setting default kernel parameters  

# predictions --
preds <- predict(svm_reg_fit, corn_test)

# plot --
corn_test |>
  cbind(preds) |> 
    ggplot() +
    geom_point(aes(x = kernel_size, y = height, color = type), shape = 1, size = 2) +
    geom_point(aes(x = kernel_size, y = .pred,  color = type), shape = 2, size = 3) +
    theme_minimal() +
    labs(title = 'Bessel Kernel SVM',
         subtitle = "corn height prediction") 

Classification

classification of corn kernel type given a specialty svm kernel

# model params --
  svm_cls_spec <- 
    svm_laplace(cost = 1, margin = 0.1, laplace_sigma = 10) |> 
    set_mode("classification") |>
    set_engine("kernlab")
  
# fit --
  svm_cls_fit <- svm_cls_spec |> fit(type ~ ., data = corn_train)

# predictions --
preds <- predict(svm_cls_fit, corn_grid, "class")
pred_grid <- corn_grid |> cbind(preds)

# plot --
corn_test |>
  ggplot() +
  geom_tile(inherit.aes = FALSE,
            data = pred_grid, 
            aes(x = kernel_size, y = height, fill = .pred_class),
            alpha = .8) + 
  geom_point(aes(x = kernel_size, y = height, color = type, shape = type), size = 3) +
  theme_minimal() +
  labs(subtitle = "Laplacian Kernel") +
  scale_fill_viridis_d() +
  scale_color_manual(values = c("violet", "cyan", "orange"))

# model params --
  svm_cls_spec <- 
    svm_cossim(cost = 1, margin = 0.1) |> 
    set_mode("classification") |>
    set_engine("kernlab")
  
# fit --
  svm_cls_fit <- svm_cls_spec |> fit(type ~ ., data = corn_train)

# predictions --
preds <- predict(svm_cls_fit, corn_grid, "class")
pred_grid <- corn_grid |> cbind(preds)

# plot --
corn_test |>
  ggplot() +
  geom_tile(inherit.aes = FALSE,
            data = pred_grid, 
            aes(x = kernel_size, y = height, fill = .pred_class),
            alpha = .8) + 
  geom_point(aes(x = kernel_size, y = height, color = type, shape = type), size = 3) +
  theme_minimal() +
  labs(subtitle = "Cossim Similarity Kernel") +
  scale_fill_viridis_d() +
  scale_color_manual(values = c("violet", "cyan", "orange"))

# model params --
  svm_cls_spec <- 
    svm_anova_rbf(cost = 1, margin = 0.1) |> 
    set_mode("classification") |>
    set_engine("kernlab")
  
# fit --
  svm_cls_fit <- svm_cls_spec |> fit(type ~ ., data = corn_train)

 Setting default kernel parameters  

# predictions --
preds <- predict(svm_cls_fit, corn_grid, "class")
pred_grid <- corn_grid |> cbind(preds)

# plot --
corn_test |>
  ggplot() +
  geom_tile(inherit.aes = FALSE,
            data = pred_grid, 
            aes(x = kernel_size, y = height, fill = .pred_class),
            alpha = .8) + 
  geom_point(aes(x = kernel_size, y = height, color = type, shape = type), size = 3) +
  theme_minimal() +
  labs(subtitle = "ANOVA RBF Kernel") +
  scale_fill_viridis_d() +
  scale_color_manual(values = c("violet", "cyan", "orange"))

# model params --
  svm_cls_spec <- 
    svm_tanimoto(cost = 1, margin = 0.1) |> 
    set_mode("classification") |>
    set_engine("kernlab")
  
# fit --
  svm_cls_fit <- svm_cls_spec |> fit(type ~ ., data = corn_train)

# predictions --
preds <- predict(svm_cls_fit, corn_grid, "class")
pred_grid <- corn_grid |> cbind(preds)

# plot --
corn_test |>
  ggplot() +
  geom_tile(inherit.aes = FALSE,
            data = pred_grid, 
            aes(x = kernel_size, y = height, fill = .pred_class),
            alpha = .8) + 
  geom_point(aes(x = kernel_size, y = height, color = type, shape = type), size = 3) +
  theme_minimal() +
  labs(subtitle = "Tanimoto Kernel") +
  scale_fill_viridis_d() +
  scale_color_manual(values = c("violet", "cyan", "orange"))

# model params --
  svm_cls_spec <- 
    svm_tstudent(cost = 1, margin = 0.1, degree = 3) |> 
    set_mode("classification") |>
    set_engine("kernlab")
  
# fit --
  svm_cls_fit <- svm_cls_spec |> fit(type ~ ., data = corn_train)

# predictions --
preds <- predict(svm_cls_fit, corn_grid, "class")
pred_grid <- corn_grid |> cbind(preds)

# plot --
corn_test |>
  ggplot() +
  geom_tile(inherit.aes = FALSE,
            data = pred_grid, 
            aes(x = kernel_size, y = height, fill = .pred_class),
            alpha = .8) + 
  geom_point(aes(x = kernel_size, y = height, color = type, shape = type), size = 3) +
  theme_minimal() +
  labs(subtitle = "T-Student Kernel") +
  scale_fill_viridis_d() +
  scale_color_manual(values = c("violet", "cyan", "orange"))

future enhancements

additional kernels are always welcome & added periodically. The more novel, the better, this is my hope for {maize}. Other enhancements include adding lssvm, rvm and/or kqr engine bindings to parsnip.

references

this package is based off the initial parsnip code, kernlab documents, and tidymodels’ developer guides. The {maize} package is a corny pun of {parsnip} & {kernels}, aw-shucks!

cheatsheets on how to register a model

• https://www.tidymodels.org/learn/develop/models/
• https://github.com/tidymodels/parsnip/blob/main/R/svm_linear.R
• https://github.com/tidymodels/parsnip/blob/main/R/svm_rbf.R
• https://github.com/tidymodels/parsnip/blob/main/R/svm_rbf_data.R

make function ideas, zzz.R,check_args,

• https://github.com/tidymodels/poissonreg/tree/main/R
• https://github.com/tidymodels/bonsai/tree/main/R

kernel parameters (kpar)

• https://github.com/cran/kernlab/blob/master/R/kernels.R
• https://www.rdocumentation.org/packages/kernlab/versions/0.9-32/topics/ksvm