Package 'deepImp'

Beer ageing volatile-compound data

Description

Concentrations of 16 volatile compounds measured in beer samples, together with an indicator distinguishing fresh from aged beer. The volatile compounds are recognised markers of beer flavour and ageing (e.g. furfural, 5-hydroxymethylfurfural, hexanal, methional-related aldehydes). The data are used to illustrate imputation of mixed continuous measurements.

Usage

data(beer)

Format

A data frame with 86 rows and 17 variables:

v3MeBual

3-methylbutanal concentration.

v3MeBuon

3-methylbutanone concentration.

v2MeBual

2-methylbutanal concentration.

vHexanal

hexanal concentration.

v2FurMeol

2-furanmethanol (furfuryl alcohol) concentration.

vHeptanal

heptanal concentration.

v2AcFur

2-acetylfuran concentration.

v5Me2Fur

5-methyl-2-furaldehyde concentration.

vEssFuEst

furanoic acid ethyl ester concentration.

v2Ac5MeFu

2-acetyl-5-methylfuran concentration.

v2PhEtal

2-phenylethanal (phenylacetaldehyde) concentration.

vNicEtEst

nicotinic acid ethyl ester concentration.

v2PhEssEt

2-phenylethyl acetate concentration.

vgNonalac

gamma-nonalactone concentration.

vFurfural

furfural concentration.

vHMF

5-hydroxymethylfurfural (HMF) concentration.

vnewold2

indicator of beer condition (fresh vs. aged).

---

Architecture configuration for neural-network imputation

Description

A backend-neutral description of the multilayer perceptron used by impNNet(). The same object is translated into a torch (and, later, keras) model.

Usage

deepimp_arch(
  hidden = c(256, 128, 64),
  dropout = 0.1,
  activation = "relu",
  batchnorm = TRUE,
  optimizer = "adam",
  learning_rate = 0.001
)

deepimp_arch_small(
  dropout = 0.1,
  activation = "relu",
  batchnorm = TRUE,
  optimizer = "adam",
  learning_rate = 0.001
)

Arguments

hidden	integer vector of hidden-layer widths; its length is the depth.
dropout	dropout rate applied after every hidden layer; a scalar in ⁠[0, 1)⁠.
activation	hidden-layer activation: one of "relu", "tanh", "sigmoid", "elu", "leaky_relu".
batchnorm	logical; apply batch normalisation after each hidden linear layer.
optimizer	one of "adam", "sgd", "rmsprop".
learning_rate	positive learning rate for the optimiser.

Value

an object of class "deepimp_arch".

See Also

impNNet(), impNNetCoDa()

Examples

deepimp_arch(hidden = c(128, 64), dropout = 0.2)

---

Extract imputed data from a deepimp object

Description

Extract imputed data from a deepimp object

Usage

getImputed(object, m = 1L, ...)

Arguments

object	a "deepimp" object from impNNet().
m	which completed dataset to return: an integer index, or "all" for the list of all imputations. With m > 1 the datasets are stochastic replicate completions, not valid multiple imputation.
...	unused.

Value

a data.frame, or a list of data.frames when m = "all".

See Also

impNNet()

---

Guess the measurement type of each variable

Description

Classifies each column as "numeric", "mixed" (semi-continuous, i.e. a spike of repeated values such as zeros plus a continuous part), "binary", "nominal", or "count". Used by impNNet() to choose the model head, and by summary() of a "deepimp" object.

Usage

guessType(x)

Arguments

x	a data.frame, data.table, or tibble.

Value

a list with indices (a type-by-variable logical matrix) and type (a character vector, one entry per column).

Author(s)

Matthias Templ

Examples

data(sleep, package = "VIM")
guessType(sleep)

---

Neural-network imputation for mixed-type data

Description

Iterative, chained imputation of numeric, count, semi-continuous, binary and nominal variables with a configurable multilayer perceptron (torch backend).

Usage

impNNet(
  data,
  arch = NULL,
  m = 1L,
  backend = c("torch", "keras"),
  vartypes = "guess",
  initialize = "knn",
  iterations = 3L,
  eps = 0.01,
  normalize = TRUE,
  epochs = 400L,
  patience = 40L,
  validation_split = 0.2,
  batch_size = 32L,
  seed = NULL,
  verbose = FALSE,
  ...
)

Arguments

data	a data.frame (tibbles/data.tables are coerced).
arch	a deepimp_arch() object, or NULL to build one from .... Supplying both arch and architecture scalars via ... is an error.
m	number of stochastic replicate completions. NOTE: with m > 1 these are stochastic replicate completions, not valid multiple imputation (no Rubin-rule inference).
backend	"torch" (default) or "keras" (optional; requires the keras3 package and a working Keras/TensorFlow backend).
vartypes	"guess" (use guessType()) or a length-ncol(data) vector.
initialize	starting values for NAs: "knn", "mean", or "hotdeck".
iterations	maximum number of chained sweeps.
eps	convergence tolerance on the standardised mean change.
normalize	standardise numeric predictors.
epochs, patience, validation_split, batch_size	training controls.
seed	optional integer seed (sets the R and backend RNGs). Exact reproducibility is guaranteed when dropout = 0; with dropout > 0 the backend's training-time mask sampling is not fully pinned by the seed in the current torch build, so repeated runs are close but may not be bit-identical.
verbose	print progress.
...	architecture scalar overrides forwarded to deepimp_arch().

Value

a "deepimp" object; read the data with getImputed().

Author(s)

Matthias Templ

See Also

deepimp_arch(), getImputed(), guessType()

Examples

if (requireNamespace("torch", quietly = TRUE) && torch::torch_is_installed()) {

  data(sleep, package = "VIM")
  imp <- impNNet(sleep, arch = deepimp_arch_small(), epochs = 5, seed = 1)
  head(getImputed(imp))

}

---

Neural-network imputation of rounded zeros in compositional data

Description

Imputes rounded zeros (values below a detection limit) in compositional data with a configurable neural network, following Templ (2021). Each part with rounded zeros is pivoted to the front, transformed to pivot log-ratio coordinates, regressed on the remaining coordinates, censored at the detection limit, and back-transformed with preservation of the observed absolute values.

Usage

impNNetCoDa(
  x,
  dl = NULL,
  label = 0,
  coda = TRUE,
  correction = c("truncate", "expectation", "none"),
  initialize = "kNNa",
  arch = NULL,
  m = 1L,
  backend = c("torch", "keras"),
  iterations = 2L,
  eps = 0.01,
  normalize = TRUE,
  epochs = 400L,
  patience = 40L,
  validation_split = 0.2,
  batch_size = 32L,
  seed = NULL,
  verbose = FALSE,
  ...
)

Arguments

x	a data.frame of compositional parts (positive values; rounded zeros marked by label).
dl	detection limits, a numeric vector of length ncol(x). Required unless correction = "none".
label	the value marking a rounded zero in x (converted to NA internally). Default 0.
coda	if TRUE (default), work in pivot log-ratio coordinates; if FALSE, impute on the raw scale (ablation).
correction	censoring of imputed values: "truncate" (default; set values above the detection limit to the limit, per Templ 2021), "expectation" (truncated-normal mean; opt-in, beyond Templ 2021), or "none" (no censoring).
initialize	starting values for the rounded zeros: "kNNa" (default, compositional kNN), "knn", "hotdeck", or "mean".
arch	a deepimp_arch() object, or NULL to build one from ....
m	number of stochastic replicate completions (not valid multiple imputation; see impNNet()).
backend	"torch" (default) or "keras" (optional; requires keras3).
iterations	maximum number of chained sweeps.
eps	convergence tolerance on the standardised mean change.
normalize	standardise numeric predictors.
epochs, patience, validation_split, batch_size	training controls.
seed	optional integer seed (sets the R and backend RNGs). Exact reproducibility is guaranteed when dropout = 0; with dropout > 0 the backend's training-time mask sampling is not fully pinned by the seed in the current torch build, so repeated runs are close but may not be bit-identical.
verbose	print progress.
...	architecture scalar overrides forwarded to deepimp_arch().

Value

a "deepimp" object; read the data with getImputed().

Author(s)

Matthias Templ

References

Templ, M. (2021) Imputation of rounded zeros for high-dimensional compositional data.

See Also

impNNet(), deepimp_arch(), getImputed()

Examples

if (requireNamespace("torch", quietly = TRUE) && torch::torch_is_installed()) {

  set.seed(1)
  x <- data.frame(a = runif(50, 5, 10), b = runif(50, 5, 10), c = runif(50, 5, 10))
  x$a[1:5] <- 0
  imp <- impNNetCoDa(x, dl = c(1, 1, 1), label = 0,
                     arch = deepimp_arch_small(), epochs = 5, seed = 1)
  head(getImputed(imp))

}

---

Construct a deepimp object

Description

Low-level constructor for the object returned by impNNet(). Most users do not call this directly; use getImputed() to read the completed data.

Usage

new_deepimp(data, imputed, arch, info = list())

Arguments

data	data.frame with missing values (original input).
imputed	list of completed data.frames (one per imputation).
arch	a deepimp_arch() object describing the network.
info	list with training metadata (backend, vartypes, convergence, ...).

Value

an object of class "deepimp".

See Also

getImputed(), impNNet()

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