Package {CKNNRLD}

Title: Clustering-Based K-Nearest Neighbor Regression for Longitudinal Data
Version: 0.2.2
Description: Implements the 'CKNNRLD' algorithm (Clustering-Based K-Nearest Neighbor Regression for Longitudinal Data) for improving K-Nearest Neighbor ('KNN') regression on longitudinal data through cluster-based partitioning and localized prediction. Offers enhanced computational efficiency and accuracy for high-volume longitudinal datasets. The acronym 'KNN' stands for K-Nearest Neighbor. References: Loeloe MS, Tabatabaei SM, Sefidkar R, Mehrparvar AH, Jambarsang S (2025). "Boosting K-nearest neighbor regression performance for longitudinal data through a novel learning approach." BMC Bioinformatics, 26, 232. <doi:10.1186/s12859-025-06205-1>.
License: GPL-3
Encoding: UTF-8
RoxygenNote: 8.0.0
Imports: Directional, graphics, grDevices, Rfast, stats
Depends: R (≥ 3.5.0)
NeedsCompilation: no
Language: en-US
Suggests: knitr, rmarkdown, testthat
LazyData: true
Packaged: 2026-07-12 06:02:17 UTC; lolo
Author: Mohammad Sadegh Loeloe [aut, cre], Seyyed Mohammad Tabatabaei [aut], Reyhane Sefidkar [aut], Amir Houshang Mehrparvar [aut], Sara Jambarsang [aut, ths]
Maintainer: Mohammad Sadegh Loeloe <mslbiostat@gmail.com>
Repository: CRAN
Date/Publication: 2026-07-13 07:20:08 UTC

Find Optimal Number of Clusters for Longitudinal Data

Description

This function determines the best number of clusters (C) for longitudinal data clustering using the elbow method (WCSS).

Usage

BestC(Y, range_clusters = 2:4, method = "kmeans")

Arguments

Y

A matrix or data frame of longitudinal outcomes (subjects x timepoints).

range_clusters

A numeric vector of cluster numbers to evaluate (e.g., 2:4).

method

Clustering method to use (currently only "kmeans").

Value

A list with best_c, criteria, and criteria_best.

Examples

set.seed(123)
n <- 20
T <- 3
y <- matrix(rnorm(n * T), nrow = n)
best_c_info <- BestC(Y = y, range_clusters = 2:3)
print(best_c_info$best_c)

Clustering-based KNN Regression for Longitudinal Data (CKNNRLD)

Description

This function implements a clustering-based KNN regression method for longitudinal data.

Usage

CKNNRLD(
  x,
  y,
  xnew = NULL,
  k = 5,
  c = 4,
  cluster_method = "kmeans",
  return_model = FALSE
)

Arguments

x

Matrix of predictors (training set).

y

Matrix of longitudinal responses (training set).

xnew

Optional matrix of predictor values for test data. If NULL, uses x.

k

Number of nearest neighbors.

c

Number of clusters.

cluster_method

Clustering method (currently "kmeans").

return_model

Logical; if TRUE, returns a model object of class CKNNRLD.

Value

If return_model = FALSE (default), a data frame with predictions. If return_model = TRUE, a list of class CKNNRLD containing model info.

Examples

set.seed(123)
n <- 20; T <- 3; d <- 2
x <- matrix(runif(n * d), nrow = n)
y <- matrix(rnorm(n * T), nrow = n)
result <- CKNNRLD(x = x, y = y, k = 3, c = 2)
head(result)

Tune CKNNRLD Model with Automatic Cluster Selection

Description

Automatically selects the best number of clusters (C) and tunes CKNNRLD.

Usage

CKNNRLD.tune(
  y,
  x,
  nfolds = 10,
  folds = NULL,
  seed = NULL,
  A = 10,
  C_range = 2:4,
  cluster_method = "kmeans"
)

Arguments

y

Matrix of longitudinal outcomes.

x

Matrix of predictor variables.

nfolds

Number of folds for cross-validation.

folds

Optional list of pre-specified fold indices.

seed

Random seed for reproducibility.

A

Maximum number of neighbors to evaluate.

C_range

Range of cluster numbers to evaluate.

cluster_method

Clustering method to use (currently only "kmeans").

Value

A list containing best_c, cluster_results, cluster_sizes, etc.

Examples

set.seed(123)
n <- 20
T <- 3
d <- 2
x <- matrix(runif(n * d), nrow = n)
y <- matrix(rnorm(n * T), nrow = n)
tune_result <- CKNNRLD.tune(
  y = y,
  x = x,
  nfolds = 3,
  A = 4,
  C_range = 2:3
)
print(tune_result$best_c)

Simulated longitudinal data for CKNNRLD example

Description

A synthetic dataset containing longitudinal responses and predictors for demonstration of the CKNNRLD package.

Usage

CKNNRLD_example

Format

A list with two elements:

x

Matrix of 100 observations and 3 predictors

y

Matrix of 100 observations and 5 time points

clusters

True cluster assignments

cluster_centers

True cluster centers

parameters

Simulation parameters

Details

The data was generated using simulateCKNNRLD(n = 100, T = 5, d = 3, C = 3) with seed 123. It contains three distinct trajectory patterns.

Examples

data(CKNNRLD_example)
str(CKNNRLD_example)
head(CKNNRLD_example$x)
head(CKNNRLD_example$y)

Standard K-Nearest Neighbor Regression for Longitudinal Data

Description

This function performs KNN regression for longitudinal data without clustering. It predicts longitudinal outcomes for new observations based on the average of their k nearest neighbors in the predictor space.

Usage

KNNRLD(xnew, y, x, k = 5)

Arguments

xnew

A matrix of predictor values for prediction (test set).

y

A matrix or data frame of longitudinal responses (training set).

x

A matrix or data frame of training predictor values.

k

Number of nearest neighbors to use. Can be a scalar or a vector.

Value

A list of matrices with predicted values for each value of k. Each matrix has dimensions nrow(xnew) x ncol(y).

Examples

set.seed(123)
n <- 20
T <- 3
d <- 2
x <- matrix(runif(n * d), nrow = n)
y <- matrix(rnorm(n * T), nrow = n)
train_idx <- sample(1:n, 14)
test_idx <- setdiff(1:n, train_idx)
pred <- KNNRLD(
  xnew = x[test_idx, ],
  y = y[train_idx, ],
  x = x[train_idx, ],
  k = 3
)
head(pred[[1]])

Tune k in KNNRLD using Cross-Validation

Description

Finds the optimal number of neighbors for KNN regression using k-fold CV.

Usage

KNNRLD.tune(
  y,
  x,
  nfolds = 10,
  folds = NULL,
  seed = NULL,
  A = 10,
  graph = FALSE
)

Arguments

y

Matrix of longitudinal outcomes.

x

Matrix of predictor variables.

nfolds

Number of cross-validation folds.

folds

Optional list of pre-specified fold indices.

seed

Optional random seed.

A

Maximum number of neighbors to evaluate.

graph

Logical; if TRUE, plots MSPE vs. k.

Value

A list containing crit, best_k, performance, and runtime.

Examples


set.seed(123)
n <- 20
T <- 3
d <- 2
x <- matrix(runif(n * d), nrow = n)
y <- matrix(rnorm(n * T), nrow = n)
tune_result <- KNNRLD.tune(
  y = y,
  x = x,
  nfolds = 3,
  A = 4
)
str(tune_result)

Benchmark CKNNRLD vs KNNRLD

Description

Compares CKNNRLD and KNNRLD on the same data.

Usage

benchmark.CKNNRLD(x, y, xnew, ytest, k = 5, c = 4)

Arguments

x

Matrix of predictors (training).

y

Matrix of responses (training).

xnew

Matrix of predictors (test).

ytest

Matrix of actual responses (test).

k

Number of neighbors.

c

Number of clusters.

Value

A data frame with benchmark results.

Examples


data(CKNNRLD_example)
benchmark.CKNNRLD(
  x = CKNNRLD_example$x,
  y = CKNNRLD_example$y,
  xnew = CKNNRLD_example$x,
  ytest = CKNNRLD_example$y,
  k = 5, c = 3
)

Extract model information from CKNNRLD

Description

Extract model information from CKNNRLD

Usage

## S3 method for class 'CKNNRLD'
coef(object, ...)

Arguments

object

A fitted CKNNRLD model object.

...

Additional arguments.

Value

A list containing model information.

Extract fitted values from CKNNRLD model

Description

Extract fitted values from CKNNRLD model

Usage

## S3 method for class 'CKNNRLD'
fitted(object, ...)

Arguments

object

A fitted CKNNRLD model object.

...

Additional arguments.

Value

A matrix of fitted values.

Variable Importance for CKNNRLD using Permutation

Description

Computes permutation-based variable importance for CKNNRLD models.

Usage

importance.CKNNRLD(
  x,
  y,
  xnew,
  ytest,
  k = 5,
  c = 4,
  nperm = 10,
  metric = "MSE",
  plot = TRUE
)

Arguments

x

Matrix of predictors (training set).

y

Matrix of longitudinal responses (training set).

xnew

Matrix of predictors for test data.

ytest

Matrix of actual responses for test data.

k

Number of nearest neighbors.

c

Number of clusters.

nperm

Number of permutations (default: 10).

metric

Performance metric: "MSE", "RMSE", or "MAE" (default: "MSE").

plot

Logical; if TRUE, plots variable importance (default: TRUE).

Value

An object of class "CKNNRLD_importance".

Examples


data(CKNNRLD_example)
imp <- importance.CKNNRLD(
  x = CKNNRLD_example$x,
  y = CKNNRLD_example$y,
  xnew = CKNNRLD_example$x,
  ytest = CKNNRLD_example$y,
  k = 5, c = 3, nperm = 5
)
print(imp)

Performance metrics for CKNNRLD models

Description

Performance metrics for CKNNRLD models

Usage

performance.CKNNRLD(object, ytest = NULL, ...)

Arguments

object

A fitted CKNNRLD model object.

ytest

Optional test set actual responses.

...

Additional arguments.

Value

A list of performance metrics.

Plot method for CKNNRLD objects

Description

Provides visualization for CKNNRLD results.

Usage

## S3 method for class 'CKNNRLD'
plot(x, y_actual = NULL, type = "clusters", ...)

Arguments

x

An object returned by CKNNRLD or a fitted CKNNRLD model.

y_actual

Optional matrix of actual longitudinal responses.

type

Type of plot: "clusters" (default), "centers", or "comparison".

...

Additional arguments passed to plot().

Value

A plot (invisibly returns NULL).

Examples


data(CKNNRLD_example)
fit <- CKNNRLD(x = CKNNRLD_example$x, y = CKNNRLD_example$y, k = 5, c = 3,
               return_model = TRUE)
plot(fit, type = "clusters")

Predict method for CKNNRLD objects

Description

Predicts longitudinal responses for new data using a fitted CKNNRLD model.

Usage

## S3 method for class 'CKNNRLD'
predict(object, newdata = NULL, ...)

Arguments

object

A fitted CKNNRLD model object (output from CKNNRLD with return_model = TRUE).

newdata

Optional matrix of new predictor values.

...

Additional arguments passed to CKNNRLD.

Value

A matrix of predicted longitudinal responses.

Examples


data(CKNNRLD_example)
fit <- CKNNRLD(x = CKNNRLD_example$x, y = CKNNRLD_example$y, k = 5, c = 3,
               return_model = TRUE)
pred <- predict(fit, newdata = CKNNRLD_example$x[1:5, ])
head(pred)

Print method for CKNNRLD objects

Description

Prints a concise summary of a fitted CKNNRLD model.

Usage

## S3 method for class 'CKNNRLD'
print(x, ...)

Arguments

x

A fitted CKNNRLD model object.

...

Additional arguments passed to print.

Value

Invisibly returns the object.

Examples


data(CKNNRLD_example)
fit <- CKNNRLD(x = CKNNRLD_example$x, y = CKNNRLD_example$y, k = 5, c = 3,
               return_model = TRUE)
print(fit)

Extract residuals from CKNNRLD model

Description

Extract residuals from CKNNRLD model

Usage

## S3 method for class 'CKNNRLD'
residuals(object, ...)

Arguments

object

A fitted CKNNRLD model object.

...

Additional arguments.

Value

A matrix of residuals.

Simulate Longitudinal Data for CKNNRLD

Description

Generates synthetic longitudinal data for testing and demonstration.

Usage

simulateCKNNRLD(
  n = 100,
  T = 5,
  d = 2,
  C = 3,
  noise_sd = 1,
  random_sd = 1,
  seed = NULL
)

Arguments

n

Number of subjects (default: 100).

T

Number of time points (default: 5).

d

Number of predictors (default: 2).

C

Number of clusters (default: 3).

noise_sd

Standard deviation of noise (default: 1).

random_sd

Standard deviation of random intercept (default: 1).

seed

Optional random seed.

Value

A list containing x, y, clusters, cluster_centers, and parameters.

Examples

sim_data <- simulateCKNNRLD(n = 50, T = 4, d = 2, C = 3)
str(sim_data)

Summary method for CKNNRLD objects

Description

Provides a detailed summary of a fitted CKNNRLD model.

Usage

## S3 method for class 'CKNNRLD'
summary(object, ytest = NULL, ...)

Arguments

object

A fitted CKNNRLD model object.

ytest

Optional test set actual responses.

...

Additional arguments.

Value

A list containing summary statistics.

Examples


data(CKNNRLD_example)
fit <- CKNNRLD(x = CKNNRLD_example$x, y = CKNNRLD_example$y, k = 5, c = 3,
               return_model = TRUE)
summary(fit)