Package 'glmtrans'

Fit a transfer learning generalized linear model (GLM) with elasticnet regularization.

Description

Fit a transfer learning generalized linear model through elastic net regularization with target data set and multiple source data sets. It also implements a transferable source detection algorithm, which helps avoid negative transfer in practice. Currently can deal with Gaussian, logistic and Poisson models.

Usage

glmtrans(
  target,
  source = NULL,
  family = c("gaussian", "binomial", "poisson"),
  transfer.source.id = "auto",
  alpha = 1,
  standardize = TRUE,
  intercept = TRUE,
  nfolds = 10,
  cores = 1,
  valid.proportion = NULL,
  valid.nfolds = 3,
  lambda = c(transfer = "lambda.1se", debias = "lambda.min", detection = "lambda.1se"),
  lambda.seq = list(transfer = NULL, debias = NULL, detection = NULL),
  detection.info = TRUE,
  target.weights = NULL,
  source.weights = NULL,
  C0 = 2,
  ...
)

Arguments

target	target data. Should be a list with elements x and y, where x indicates a predictor matrix with each row/column as a(n) observation/variable, and y indicates the response vector.
source	source data. Should be a list with some sublists, where each of the sublist is a source data set, having elements x and y with the same meaning as in target data.
family	response type. Can be "gaussian", "binomial" or "poisson". Default = "gaussian". "gaussian": Gaussian distribution. "binomial": logistic distribution. When family = "binomial", the input response in both target and source should be 0/1. "poisson": poisson distribution. When family = "poisson", the input response in both target and source should be non-negative.
transfer.source.id	transferable source indices. Can be either a subset of {1, ..., length(source)}, "all" or "auto". Default = "auto". a subset of {1, ..., length(source)}: only transfer sources with the specific indices. "all": transfer all sources. "auto": run transferable source detection algorithm to automatically detect which sources to transfer. For the algorithm, refer to the documentation of function source_detection.
alpha	the elasticnet mixing parameter, with $0 \leq \alpha \leq 1$. The penality is defined as $(1-\alpha)/2||\beta||_2^2+\alpha ||\beta||_1$ . alpha = 1 encodes the lasso penalty while alpha = 0 encodes the ridge penalty. Default = 1.
standardize	the logical flag for x variable standardization, prior to fitting the model sequence. The coefficients are always returned on the original scale. Default is TRUE.
intercept	the logical indicator of whether the intercept should be fitted or not. Default = TRUE.
nfolds	the number of folds. Used in the cross-validation for GLM elastic net fitting procedure. Default = 10. Smallest value allowable is nfolds = 3.
cores	the number of cores used for parallel computing. Default = 1.
valid.proportion	the proportion of target data to be used as validation data when detecting transferable sources. Useful only when transfer.source.id = "auto". Default = NULL, meaning that the cross-validation will be applied.
valid.nfolds	the number of folds used in cross-validation procedure when detecting transferable sources. Useful only when transfer.source.id = "auto" and valid.proportion = NULL. Default = 3.
lambda	a vector indicating the choice of lambdas in transferring, debiasing and detection steps. Should be a vector with names "transfer", "debias", and "detection", each component of which can be either "lambda.min" or "lambda.1se". Component transfer is the lambda (the penalty parameter) used in transferrring step. Component debias is the lambda used in debiasing step. Component detection is the lambda used in the transferable source detection algorithm. Default choice of lambda.transfer and lambda.detection are "lambda.1se", while default lambda.debias = "lambda.min". If the user wants to change the default setting, input a vector with corresponding lambda.transfer/lambda.debias/lambda.detection names and corresponding values. Examples: lambda = list(transfer = "lambda.1se", debias = "lambda.min", detection = "lambda.1se"); lambda = list(transfer = 1, debias = 0.5, detection = 1). "lambda.min": value of lambda that gives minimum mean cross-validated error in the sequence of lambda. "lambda.1se": largest value of lambda such that error is within 1 standard error of the minimum.
lambda.seq	the sequence of lambda candidates used in the algorithm. Should be a list of three vectors with names "transfer", "debias", and "detection". Default = list(transfer = NULL, debias = NULL, detection = NULL). "NULL" means the algorithm will determine the sequence automatically, based on the same method used in cv.glmnet.
detection.info	the logistic flag indicating whether to print detection information or not. Useful only when transfer.source.id = "auto". Default = TURE.
target.weights	weight vector for each target instance. Should be a vector with the same length of target response. Default = NULL, which makes all instances equal-weighted.
source.weights	a list of weight vectors for the instances from each source. Should be a list with the same length of the number of sources. Default = NULL, which makes all instances equal-weighted.
C0	the constant used in the transferable source detection algorithm. See Algorithm 2 in Tian, Y. & Feng, Y. (2023). Default = 2.
...	additional arguments.

Value

An object with S3 class "glmtrans".

beta	the estimated coefficient vector.
family	the response type.
transfer.source.id	the transferable source index. If in the input, transfer.source.id = 1:length(source) or transfer.source.id = "all", then the outputed transfer.source.id = 1:length(source). If the inputed transfer.source.id = "auto", only transferable source detected by the algorithm will be outputed.
fitting.list	a list of other parameters of the fitted model.

• w_a: the estimator obtained from the transferring step.

• delta_a: the estimator obtained from the debiasing step.

• target.valid.loss: the validation (or cross-validation) loss on target data. Only available when transfer.source.id = "auto".

• source.loss: the loss on each source data. Only available when transfer.source.id = "auto".

• threshold: the threshold to determine transferability. Only available when transfer.source.id = "auto".

References

Tian, Y., & Feng, Y. (2023). Transfer learning under high-dimensional generalized linear models. Journal of the American Statistical Association, 118(544), 2684-2697.

Li, S., Cai, T.T. & Li, H. (2020). Transfer learning for high-dimensional linear regression: Prediction, estimation, and minimax optimality. arXiv preprint arXiv:2006.10593.

Friedman, J., Hastie, T. & Tibshirani, R. (2010). Regularization paths for generalized linear models via coordinate descent. Journal of statistical software, 33(1), p.1.

Zou, H. & Hastie, T. (2005). Regularization and variable selection via the elastic net. Journal of the royal statistical society: series B (statistical methodology), 67(2), pp.301-320.

Tibshirani, R. (1996). Regression shrinkage and selection via the lasso. Journal of the Royal Statistical Society: Series B (Methodological), 58(1), pp.267-288.

See Also

predict.glmtrans, source_detection, models, plot.glmtrans, cv.glmnet, glmnet.

Examples

set.seed(0, kind = "L'Ecuyer-CMRG")

# fit a linear regression model
D.training <- models("gaussian", type = "all", n.target = 100, K = 2, p = 500)
D.test <- models("gaussian", type = "target", n.target = 500, p = 500)
fit.gaussian <- glmtrans(D.training$target, D.training$source)
y.pred.glmtrans <- predict(fit.gaussian, D.test$target$x)

# compare the test MSE with classical Lasso fitted on target data
library(glmnet)
fit.lasso <- cv.glmnet(x = D.training$target$x, y = D.training$target$y)
y.pred.lasso <- predict(fit.lasso, D.test$target$x)

mean((y.pred.glmtrans - D.test$target$y)^2)
mean((y.pred.lasso - D.test$target$y)^2)


# fit a logistic regression model
D.training <- models("binomial", type = "all", n.target = 100, K = 2, p = 500)
D.test <- models("binomial", type = "target", n.target = 500, p = 500)
fit.binomial <- glmtrans(D.training$target, D.training$source, family = "binomial")
y.pred.glmtrans <- predict(fit.binomial, D.test$target$x, type = "class")

# compare the test error with classical Lasso fitted on target data
library(glmnet)
fit.lasso <- cv.glmnet(x = D.training$target$x, y = D.training$target$y, family = "binomial")
y.pred.lasso <- as.numeric(predict(fit.lasso, D.test$target$x, type = "class"))

mean(y.pred.glmtrans != D.test$target$y)
mean(y.pred.lasso != D.test$target$y)


# fit a Poisson regression model
D.training <- models("poisson", type = "all", n.target = 100, K = 2, p = 500)
D.test <- models("poisson", type = "target", n.target = 500, p = 500)
fit.poisson <- glmtrans(D.training$target, D.training$source, family = "poisson")
y.pred.glmtrans <- predict(fit.poisson, D.test$target$x, type = "response")

# compare the test MSE with classical Lasso fitted on target data
fit.lasso <- cv.glmnet(x = D.training$target$x, y = D.training$target$y, family = "poisson")
y.pred.lasso <- as.numeric(predict(fit.lasso, D.test$target$x, type = "response"))

mean((y.pred.glmtrans - D.test$target$y)^2)
mean((y.pred.lasso - D.test$target$y)^2)

---

Calculate asymptotic confidence intervals based on desparsified Lasso and two-step transfer learning method.

Description

Given the point esimate of the coefficient vector from glmtrans, calculate the asymptotic confidence interval of each component. The detailed inference algorithm can be found as Algorithm 3 in the latest version of Tian, Y. and Feng, Y., 2021. The algorithm is consructed based on a modified version of desparsified Lasso (Van de Geer, S. et al, 2014; Dezeure, R. et al, 2015).

Usage

glmtrans_inf(
  target,
  source = NULL,
  family = c("gaussian", "binomial", "poisson"),
  beta.hat = NULL,
  nodewise.transfer.source.id = "all",
  cores = 1,
  level = 0.95,
  intercept = TRUE,
  ...
)

Arguments

target	target data. Should be a list with elements x and y, where x indicates a predictor matrix with each row/column as a(n) observation/variable, and y indicates the response vector.
source	source data. Should be a list with some sublists, where each of the sublist is a source data set, having elements x and y with the same meaning as in target data.
family	response type. Can be "gaussian", "binomial" or "poisson". Default = "gaussian". "gaussian": Gaussian distribution. "binomial": logistic distribution. When family = "binomial", the input response in both target and source should be 0/1. "poisson": poisson distribution. When family = "poisson", the input response in both target and source should be non-negative.
beta.hat	initial estimate of the coefficient vector (the intercept should be the first component). Can be from the output of function glmtrans.
nodewise.transfer.source.id	transferable source indices in the infernce (the set A in Algorithm 3 of Tian, Y. and Feng, Y., 2021). Can be either a subset of {1, ..., length(source)}, "all" or NULL. Default = "all". a subset of {1, ..., length(source)}: only transfer sources with the specific indices. "all": transfer all sources. NULL: don't transfer any sources and only use target data.
cores	the number of cores used for parallel computing. Default = 1.
level	the level of confidence interval. Default = 0.95. Note that the level here refers to the asymptotic level of confidence interval of a single component rather than the multiple intervals.
intercept	whether the model includes the intercept or not. Default = TRUE. Should be set as TRUE if the intercept of beta.hat is not zero.
...	additional arguments.

Value

a list of output. b.hat = b.hat, beta.hat = beta.hat, CI = CI, var.est = var.est

b.hat	the center of confidence intervals. A p-dimensional vector, where p is the number of predictors.
beta.hat	the initial estimate of the coefficient vector (the same as input).
CI	confidence intervals (CIs) with the specific level. A p by 3 matrix, where three columns indicate the center, lower limit and upper limit of CIs, respectively. Each row represents a coefficient component.
var.est	the estimate of variances in the CLT (Theta transpose times Sigma times Theta, in section 2.5 of Tian, Y. and Feng, Y., 2021). A p-dimensional vector, where p is the number of predictors.

References

Tian, Y., & Feng, Y. (2023). Transfer learning under high-dimensional generalized linear models. Journal of the American Statistical Association, 118(544), 2684-2697.

Van de Geer, S., Bühlmann, P., Ritov, Y.A. & Dezeure, R. (2014). On asymptotically optimal confidence regions and tests for high-dimensional models. The Annals of Statistics, 42(3), pp.1166-1202.

Dezeure, R., Bühlmann, P., Meier, L. & Meinshausen, N. (2015). High-dimensional inference: confidence intervals, p-values and R-software hdi. Statistical science, pp.533-558.

See Also

glmtrans.

Examples

## Not run: 
set.seed(0, kind = "L'Ecuyer-CMRG")

# generate binomial data
D.training <- models("binomial", type = "all", K = 2, p = 200)

# fit a logistic regression model via two-step transfer learning method
fit.binomial <- glmtrans(D.training$target, D.training$source, family = "binomial")

# calculate the CI based on the point estimate from two-step transfer learning method
fit.inf <- glmtrans_inf(target = D.training$target, source = D.training$source,
family = "binomial", beta.hat = fit.binomial$beta, cores = 2)

## End(Not run)

---

Generate data from Gaussian, logistic and Poisson models.

Description

Generate data from Gaussian, logistic and Poisson models used in the simulation part of Tian, Y., & Feng, Y. (2023).

Usage

models(
  family = c("gaussian", "binomial", "poisson"),
  type = c("all", "source", "target"),
  cov.type = 1,
  h = 5,
  K = 5,
  n.target = 200,
  n.source = rep(100, K),
  s = 5,
  p = 500,
  Ka = K
)

Arguments

family	response type. Can be "gaussian", "binomial" or "poisson". Default = "gaussian". "gaussian": Gaussian distribution. "binomial": logistic distribution. When family = "binomial", the input response in both target and source should be 0/1. "poisson": poisson distribution. When family = "poisson", the input response in both target and source should be non-negative.
type	the type of generated data. Can be "all", "source" or "target". "all": generate a list with a target data set of size n.target and K source data set of size n.source. "source": generate a list with K source data set of size n.source. "target": generate a list with a target data set of size n.target.
cov.type	the type of covariates. Can be 1 or 2 (numerical). If it equals to 1, the predictors will be generated from the distribution used in Section 4.1.1 (Ah-Trans-GLM) in the latest version of Tian, Y., & Feng, Y. (2023). If it equals to 2, the predictors will be generated from the distribution used in Section 4.1.2 (When transferable sources are unknown).
h	measures the deviation ($l_1$-norm) of transferable source coefficient from the target coefficient. Default = 5.
K	the number of source data sets. Default = 5.
n.target	the sample size of target data. Should be a positive integer. Default = 100.
n.source	the sample size of each source data. Should be a vector of length K. Default is a K-vector with all elements 150.
s	how many components in the target coefficient are non-zero, which controls the sparsity of target problem. Default = 15.
p	the dimension of data. Default = 1000.
Ka	the number of transferable sources. Should be an integer between 0 and K. Default = K.

Value

a list of data sets which depend on the value of type.

• type = "all": a list of two components named "target" and "source" storing the target and source data, respectively. Component source is a list containing K components with the first Ka ones h-transferable and the remaining ones h-nontransferable. The target data set and each source data set have components "x" and "y", as the predictors and responses, respectively.

• type = "source": a list with a signle component "source". This component contains a list of K components with the first Ka ones h-transferable and the remaining ones h-nontransferable. Each source data set has components "x" and "y", as the predictors and responses, respectively.

• type = "target": a list with a signle component "target". This component contains another list with components "x" and "y", as the predictors and responses of target data, respectively.

References

Tian, Y., & Feng, Y. (2023). Transfer learning under high-dimensional generalized linear models. Journal of the American Statistical Association, 118(544), 2684-2697.

See Also

glmtrans.

Examples

set.seed(0, kind = "L'Ecuyer-CMRG")

D.all <- models("binomial", type = "all")
D.target <- models("binomial", type = "target")
D.source <- models("binomial", type = "source")

---

Visualize the losses of different sources and the threshold to determine transferability.

Description

Plot the losses of different sources and the threshold to determine transferability for object with class "glmtrans" or "glmtrans_source_detection".

Usage

## S3 method for class 'glmtrans'
plot(x, ...)

Arguments

x	an object from class "glmtrans" or "glmtrans_source_detection", which are the output of functions glmtrans and source_detection, respectively.
...	additional arguments that can be passed to ggplot function.

Value

a "ggplot" visualization with the transferable threshold and losses of different sources.

References

Tian, Y., & Feng, Y. (2023). Transfer learning under high-dimensional generalized linear models. Journal of the American Statistical Association, 118(544), 2684-2697.

See Also

glmtrans, source_detection, ggplot.

Examples

set.seed(1, kind = "L'Ecuyer-CMRG")

D.training <- models("gaussian", K = 2, p = 500, Ka = 1)

# plot for class "glmtrans"
fit.gaussian <- glmtrans(D.training$target, D.training$source)
plot(fit.gaussian)


# plot for class "glmtrans_source_detection"
detection.gaussian <- source_detection(D.training$target, D.training$source)
plot(detection.gaussian)

---

Predict for new data from a "glmtrans" object.

Description

Predict from a "glmtrans" object based on new observation data. There are various types of output available.

Usage

## S3 method for class 'glmtrans'
predict(
  object,
  newx,
  type = c("link", "response", "class", "integral response"),
  ...
)

Arguments

object	an object from class "glmtrans", which comes from the output of function glmtrans.
newx	the matrix of new values for predictors at which predictions are to be made. Should be in accordance with the data for training object.
type	the type of prediction. Default = "link".
...	additional arguments. "link": the linear predictors. When family = "gaussian", it is the same as the predicited responses. "response": gives the predicited probabilities when family = "binomial", the predicited mean when family = "poisson", and the predicited responses when family = "gaussian". "class": the predicited 0/1 responses for lositic distribution. Applies only when family = "binomial". "integral response": the predicited integral response for Poisson distribution. Applies only when family = "poisson".

Value

the predicted result on new data, which depends on type.

References

Tian, Y., & Feng, Y. (2023). Transfer learning under high-dimensional generalized linear models. Journal of the American Statistical Association, 118(544), 2684-2697.

See Also

glmtrans.

Examples

set.seed(1, kind = "L'Ecuyer-CMRG")

# fit a logistic model
D.training <- models("binomial", type = "all", K = 1, p = 500)
D.test <- models("binomial", type = "target", n.target = 10, p = 500)
fit.binomial <- glmtrans(D.training$target, D.training$source, family = "binomial")

predict(fit.binomial, D.test$target$x, type = "link")
predict(fit.binomial, D.test$target$x, type = "response")
predict(fit.binomial, D.test$target$x, type = "class")


# fit a Poisson model
D.training <- models("poisson", type = "all", K = 1, p = 500)
D.test <- models("poisson", type = "target", n.target = 10, p = 500)
fit.poisson <- glmtrans(D.training$target, D.training$source, family = "poisson")

predict(fit.poisson, D.test$target$x, type = "response")
predict(fit.poisson, D.test$target$x, type = "integral response")

---

Print a fitted "glmtrans" object.

Description

Similar to the usual print methods, this function summarizes results from a fitted "glmtrans" object.

Usage

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

Arguments

x	fitted "glmtrans" model object.
...	additional arguments.

Value

No value is returned.

See Also

glmtrans.

Examples

set.seed(1, kind = "L'Ecuyer-CMRG")

# fit a linear model
D.training <- models("gaussian", K = 2, p = 500)
fit.gaussian <- glmtrans(D.training$target, D.training$source)

fit.gaussian

---

Transferable source detection for GLM transfer learning algorithm.

Description

Detect transferable sources from multiple source data sets. Currently can deal with Gaussian, logistic and Poisson models.

Usage

source_detection(
  target,
  source = NULL,
  family = c("gaussian", "binomial", "poisson"),
  alpha = 1,
  standardize = TRUE,
  intercept = TRUE,
  nfolds = 10,
  cores = 1,
  valid.nfolds = 3,
  lambda = "lambda.1se",
  lambda.seq = NULL,
  detection.info = TRUE,
  target.weights = NULL,
  source.weights = NULL,
  C0 = 2,
  ...
)

Arguments

target	target data. Should be a list with elements x and y, where x indicates a predictor matrix with each row/column as a(n) observation/variable, and y indicates the response vector.
source	source data. Should be a list with some sublists, where each of the sublist is a source data set, having elements x and y with the same meaning as in target data.
family	response type. Can be "gaussian", "binomial" or "poisson". Default = "gaussian". "gaussian": Gaussian distribution. "binomial": logistic distribution. When family = "binomial", the input response in both target and source should be 0/1. "poisson": poisson distribution. When family = "poisson", the input response in both target and source should be non-negative.
alpha	the elasticnet mixing parameter, with $0 \leq \alpha \leq 1$. The penality is defined as $(1-\alpha)/2||\beta||_2^2+\alpha ||\beta||_1$ . alpha = 1 encodes the lasso penalty while alpha = 0 encodes the ridge penalty. Default = 1.
standardize	the logical flag for x variable standardization, prior to fitting the model sequence. The coefficients are always returned on the original scale. Default is TRUE.
intercept	the logical indicator of whether the intercept should be fitted or not. Default = TRUE.
nfolds	the number of folds. Used in the cross-validation for GLM elastic net fitting procedure. Default = 10. Smallest value allowable is nfolds = 3.
cores	the number of cores used for parallel computing. Default = 1.
valid.nfolds	the number of folds used in cross-validation procedure when detecting transferable sources. Useful only when transfer.source.id = "auto". Default = 3.
lambda	lambda (the penalty parameter) used in the transferable source detection algorithm. Can be either "lambda.min" or "lambda.1se". Default = "lambda.1se".
lambda.seq	the sequence of lambda candidates used in the algorithm. Should be a vector of numerical values. Default = NULL, which means the algorithm will determine the sequence automatically, based on the same method used in cv.glmnet.
detection.info	the logistic flag indicating whether to print detection information or not. Useful only when transfer.source.id = "auto". Default = TURE.
target.weights	weight vector for each target instance. Should be a vector with the same length of target response. Default = NULL, which makes all instances equal-weighted.
source.weights	a list of weight vectors for the instances from each source. Should be a list with the same length of the number of sources. Default = NULL, which makes all instances equal-weighted.
C0	the constant used in the transferable source detection algorithm. See Algorithm 2 in Tian, Y. and Feng, Y., 2021. Default = 2. "lambda.min": value of lambda that gives minimum mean cross-validated error in the sequence of lambda. "lambda.1se": largest value of lambda such that error is within 1 standard error of the minimum.
...	additional arguments.

Value

An object with S3 class "glmtrans_source_detection".

transfer.source.id	the index of transferable sources.
source.loss	the loss on each source data. Only available when transfer.source.id = "auto".
target.valid.loss	the validation (or cross-validation) loss on target data. Only available when transfer.source.id = "auto".
threshold	the threshold to determine transferability. Only available when transfer.source.id = "auto".

Note

source.loss and threshold outputed by source_detection can be visualized by function plot.glmtrans.

References

Tian, Y., & Feng, Y. (2023). Transfer learning under high-dimensional generalized linear models. Journal of the American Statistical Association, 118(544), 2684-2697.

Li, S., Cai, T.T. & Li, H., (2020). Transfer learning for high-dimensional linear regression: Prediction, estimation, and minimax optimality. arXiv preprint arXiv:2006.10593.

Friedman, J., Hastie, T. & Tibshirani, R., (2010). Regularization paths for generalized linear models via coordinate descent. Journal of statistical software, 33(1), p.1.

Zou, H. & Hastie, T., (2005). Regularization and variable selection via the elastic net. Journal of the royal statistical society: series B (statistical methodology), 67(2), pp.301-320.

Tibshirani, R., (1996). Regression shrinkage and selection via the lasso. Journal of the Royal Statistical Society: Series B (Methodological), 58(1), pp.267-288.

See Also

glmtrans, predict.glmtrans, models, plot.glmtrans, cv.glmnet, glmnet.

Examples

set.seed(0, kind = "L'Ecuyer-CMRG")

# study the linear model
D.training <- models("gaussian", type = "all", K = 2, p = 500, Ka = 1, n.target = 100, cov.type = 2)
detection.gaussian <- source_detection(D.training$target, D.training$source)
detection.gaussian$transfer.source.id


# study the logistic model
D.training <- models("binomial", type = "all", K = 2, p = 500, Ka = 1, n.target = 100, cov.type = 2)
detection.binomial <- source_detection(D.training$target, D.training$source,
family = "binomial", cores = 2)
detection.binomial$transfer.source.id


# study Poisson model
D.training <- models("poisson", type = "all", K = 2, p = 500, Ka = 1, n.target = 100, cov.type = 2)
detection.poisson <- source_detection(D.training$target, D.training$source,
family = "poisson", cores = 2)
detection.poisson$transfer.source.id

---