Changes in version 1.1.5 (2021-10-20)                  

Major changes

  - Revise the help documentation for the function OptStiefelGBB.R.
  - The Journal of Statistical Software paper accompanying this package
    has been published.

                 Changes in version 1.1.4 (2021-06-25)                  

Major changes

  - We change the title from Tensor Regression with Envelope Structure
    and Three Generic Envelope Estimation Approaches'' to Tensor
    Regression with Envelope Structure''.

Minor change

  - Revert res <- kroncov(En) to res <- try(kroncov(En)) in function
    TRR.fit, which is forgotten to be reverted in last version.

                 Changes in version 1.1.3 (2020-10-16)                  

Major changes

  - Replace the base::norm(x, 'F') function with sqrt(sum(x^2)) for some
    matrix x.
  - In the Data segment of the printout of the tensor object, instead of
    just the first few elements, the summarized results of all elements
    are printed.

Minor changes

  - Add more output information returned from OptManiMulitBallGBB() to
    the output of ballGBB1D().

                 Changes in version 1.1.2 (2020-07-23)                  

Major changes

  - Renaming: TRR_sim -> TRRsim; TPR_sim -> TPRsim; TensEnv_dim ->
    TRRdim; ballGBB1D_bic -> oneD_bic; TensPLS_cv2d3d -> TPRdim;
    OptimballGBB1D -> OptM1D; EnvMU -> simplsMU
  - Deprecate:
  - plot.Tenv:
      - Correct the direction of y axis. The coordinates of x and y
        increase from left to right, top to bottom;
      - Add arguments xlab = "", ylab = "", axes = TRUE, ask = TRUE,
        remove arguments xticks, yticks. axes is a logical value
        specifying whether the axes should be drawn. If ask = TRUE, user
        is prompted before the second plot is shown (if exists).
  - ECD, simplsMU, manifold1D, manifoldFG, OptM1D, OptMFG: Change
    optional arguments like maxiter, tol, to three dots ...
  - fun1D, get_ini1D, ballGBB1D, OptManiMulitBallGBB: Collected into
    file "1Dfunction.R". Help documentation are no longer supported.
  - MenvU_sim: An option wishart = FALSE is provided to return the
    population matrices M and U. Other argument like jitter is also
    provided which adds an scaler matrix to M to ensures it
    positive-definiteness.
  - PMSE: Calculates the prediction and mean squared error for both TRR
    and TPR models.
  - kroncov: Add convergence criterion tol and the maximal iteration
    maxiter.

Minor changes

  - OptStiefelGBB: Hide out from the output.
  - manifoldFG: Set default value for Gamma_init.
  - ttt.R: Change arguments X,Y to x,y.
  - oneD_bic: Add the estimated envelope basis Gamma to the output.
  - TRRdim: Output the mean squared error using the selected envelope
    basis.
  - TRRdim, oneD_bic: Argument multiD is changed to C to comply with the
    paper Zhang X, Mai Q (2018). "Model-Free Envelope Dimension
    Selection." Electronic Journal of Statistics.

New functions

  - OptMFG: New FG optimization function encapsulating the core function
    OptStiefelGBB.
  - show: overloads show in package rTensor. With the overloaded show,
    only the first 6 elements of tensor is printed out.

Bugs

  - In documentation of subspace(), the formula of subspace distance
    should be ||P_{A} - P_{B}||_F/√{2d}.
  - Fix bat dataset where x was not binary.

                 Changes in version 1.1.1 (2020-02-05)                  

Major changes

  - Lists or environments data structures are also acceptable as a whole
    in TRR.fit() and TPR.fit(). They can be passed to argument x.
  - Since the variance-covariance matrix is not available for Tenv class
    object, we remove S3 methods vcov.Tenv(). Use function std_err() if
    the standard error for the tensor coefficient from TRR.fit() is
    desired.
  - Improved the computation efficiency by adopting cholesky
    decomposition in matrix inversion and the calculation of the square
    root of a matrix.
  - Add a real data set EEG. Refer to R help documentation for more
    details
  - Add a new feature to predict.Tenv(): if the argument newdata is
    missing, the fitted values from the fitted model is returned.

Minor changes

  - Change arguments Xn and Yn in all functions to x and y in accordance
    with other popular functions, e.g., lm(), glm(), etc.
  - plot.Tenv(): Change the name of argument thrd to level.
  - kroncov: Data Tn is centered before the estimation.

                 Changes in version 1.1.0 (2019-11-17)                  

Small changes

  - Add some references in Description field in file DESCRIPTION
  - Fix the document of summary.Tenv.
  - Remove the parameter ask in plot.Tenv.
  - Add envelope basis Gamma list into bat and square datasets.
  - Change the names of some parameters, like bic_max to maxdim in
    TensEnv_dim, max_iter to maxiter in manifold1D, epsilon to tol in
    ECD, G_ini to Gamma_init in manifoldFG, G_hat to Gamma in
    manifoldFG, Yhat to pred in PMSE.
  - Rename TRR, TPR as TRR.fit, TPR,fit.

S3 methods

  - print.Tenv: Prints the call, coefficients from TPR and TRR, make the
    output more concise.
  - print.summary.Tenv: Print call, dimensions of X, Y, sample size,
    mse, the coefficient and p_value. (invoked implicitly when there is
    no assignment of summary.Tenv).

                 Changes in version 1.0.0 (2019-10-22)                  

Major changes

  - Switch the arguments Xn and Yn in functions: TensEnv_dim,
    TensPLS_cv2d3d, Tenv, Tenv_Pval, TPR and TRR.
  - Removed package mvtnorm in DESCRIPTION, it is not used in the
    package.
  - Move all the packages in Depends in DESCRIPTION to Imports except
    for ManifoldOptim.
  - Add examples to some functions: PMSE, TensEnv_dim, TensPLS_cv2d3d,
    Tenv_Pval.
  - Add simulated data "bat" and "square" with which users can quickly
    verify the functions in the package.

# Usage
> data("bat")
> data("square")

  - TPR, TRR:
      - Change the output names of some functions. E.g., Bhat in the
        object returned from TPR and TRR is renamed as coefficients.
      - Append fitted.values and residuals into the output.
      - More robust to the input type: Yn can be vector or matrix and Xn
        can be matrix, array or tensor for TPR, Xn can be vector or
        matrix and Yn can be matrix, array or tensor for TRR.
      - Incorporate FG_TRR and FG_TPR into TRR and TPR. Add one more
        option for method, "FG". Also add argument Gamma_init for "FG"
        method.
  - Tenv_Pval: Change the data type of outputs from array to tensor.
    Change the name se_mat to se.
  - PMSE: Rewrite PMSE. Xn can be matrix, array or tensor, Yn can be
    vector or matrix, and Bhat can be vector, matrix, array or tensor as
    long as the dimensions match the ones of Xn and Yn.
  - TRR_sim, TPR_sim: Add two simulation functions to generate data used
    in TRR and TPR which can help user quickly test the functions.

S3 methods

Construct S3 object for TRR and TPR with class attribute "Tenv"

> data("bat")
> fit <- TRR(bat$Xn, bat$Yn, method = "standard")
> class(fit)
> [1] "Tenv"

  - predict.Tenv: Make predictions of new data.
  - summary.Tenv: Append dimensions of X,Y, sample size, mse, p_val and
    s.e. to the output object from TPR and TRR.
  - plot.Tenv: Draw the plot of coefficients from TRR and TPR, and draw
    p_val plot from TRR.
  - vcov.Tenv: No covariance for coefficients. But for TRR, we print the
    standard error for coefficients.
  - fitted.default: Calculates the fitted Y for TPR and TRR separately.
  - residuals.default: Calculate Y minus fitted Y for TPR and TRR
  - coef.default: Print the coefficients for TPR and TRR.

Deprecated functions

  - FG_TPR, FG_TRR

Help pages for deprecated functions are available at
help("TRES-deprecated").

Bug fixed

  - Default value u=NULL for TPR and TRR.
  - Default value maxdim=10 and nfold=5 for TensPLS_cv2d3d
  - PMSE: now accept tensor Xn