Description Usage Arguments Details Value Author(s) References See Also Examples
Let (x_1, y_1), …, (x_n, y_n) denote the n measurements of the predictor and response, where x_i\in R^p and y_i \in R. The model assumes that these measurements are a realization of n independent copies of the random vector (X,Y)', where
X = μ_X + Γ β\{f(Y) - μ_f\}+ ε,
μ_X\in R^p; Γ\in R^{p\times d} with rank d; β \in R^{d\times r} with rank d; f: R \rightarrow R^r is a known vector valued function; μ_f = E\{f(Y)\}; ε \sim N_p(0, Δ); and Y is independent of ε. The central subspace is Δ^{-1} {\rm span}(Γ).
This function computes estimates of these model parameters by imposing constraints for identifiability. The mean parameters μ_X and μ_f are estimated with \bar x = n^{-1}∑_{i=1}^n x_i and \bar f = n^{-1} ∑_{i=1}^n f(y_i). Let \widehatΦ = n^{-1}∑_{i=1}^{n} \{f(y_i) - \bar f\}\{f(y_i) - \bar f\}', which we require to be positive definite. Given a user-specified weight matrix \widehat W, let
(\widehatΓ, \widehatβ) = \arg\min_{G\in R^{p\times d}, B \in R^{d\times r}} ∑_{i=1}^n [x_i - \bar x - GB\{f(y_i) - \bar f\}]'\widehat W [x_i - \bar x - GB\{f(y_i) - \bar f\}],
subject to the constraints that G'\widehat W G is diagonal and B \widehatΦ B' = I. The sufficient reduction estimate \widehat R: R^p \rightarrow R^d is defined by
\widehat R(x) = (\widehatΓ'\widehat W \widehatΓ)^{-1} \widehatΓ' \widehat W(x - \bar x).
1 2 3 |
X |
The predictor matrix with n rows and p columns. The ith row is x_i defined above. |
y |
The vector of measured responses with n entries. The ith entry is y_i defined above. |
r |
When polynomial basis functions are used (which is the case when |
d |
The dimension of the central subspace defined above. This must be specified by the user
when |
F.user |
A matrix with n rows and r columns, where the ith row is f(y_i) defined above. This argument is optional, and will typically be used when polynomial basis functions are not desired. |
weight.type |
The type of weight matrix estimate \widehat W to use.
Let \widehatΔ be the observed residual sample covariance matrix for the multivariate
regression of
|
lam.vec |
A vector of candidate tuning parameter values to use when |
kfold |
The number of folds to use in cross-validation to select the optimal tuning parameter when |
silent |
Logical. When |
qrtol |
The tolerance for calls to |
cov.tol |
The convergence tolerance for the QUIC algorithm used when |
cov.maxit |
The maximum number of iterations allowed for the QUIC algorithm used when |
NPERM |
The number of permutations to used in the sequential permutation testing procedure to select d.
Only used when |
level |
The significance level to use to terminate the sequential permutation testing procedure to select d. |
See Cook, Forzani, and Rothman (2012) more information.
A list with
Gamhat |
this is \widehatΓ described above. |
bhat |
this is \widehatβ described above. |
Rmat |
this is \widehat W\widehatΓ(\widehatΓ'\widehat W \widehatΓ)^{-1}. |
What |
this is \widehat W described above. |
d |
this is d described above. |
r |
this is r described above. |
GWG |
this is \widehatΓ'\widehat W \widehatΓ |
fc |
a matrix with n rows and r columns where the ith row is f(y_i) - \bar f. |
Xc |
a matrix with n rows and p columns where the ith row is x_i - \bar x. |
y |
the vector of n response measurements. |
mx |
this is \bar x described above. |
mf |
this is \bar f described above. |
best.lam |
this is selected tuning parameter value used when |
lam.vec |
this is the vector of candidate tuning parameter values used when
|
err.vec |
this is the vector of validation errors from cross validation, one error for each entry in |
test.info |
a dataframe that summarizes the results from the sequential testing procedure. Will be |
Adam J. Rothman
Cook, R. D., Forzani, L., and Rothman, A. J. (2012). Estimating sufficient reductions of the predictors in abundant high-dimensional regressions. Annals of Statistics 40(1), 353-384.
Friedman, J., Hastie, T., and Tibshirani R. (2008). Sparse inverse covariance estimation with the lasso. Biostatistics 9(3), 432-441.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | set.seed(1)
n=20
p=30
d=2
y=sqrt(12)*runif(n)
Gam=matrix(rnorm(p*d), nrow=p, ncol=d)
beta=diag(2)
E=matrix(0.5*rnorm(n*p), nrow=n, ncol=p)
V=matrix(c(1, sqrt(12), sqrt(12), 12.8), nrow=2, ncol=2)
tmp=eigen(V, symmetric=TRUE)
V.msqrt=tcrossprod(tmp$vec*rep(tmp$val^(-0.5), each=2), tmp$vec)
Fyc=cbind(y-sqrt(3),y^2-4)%*%V.msqrt
X=0+Fyc%*%t(beta)%*%t(Gam) + E
fit=fit.pfc(X=X, y=y, r=3, weight.type="sample")
## display hypothesis testing information for selecting d
fit$test.info
## make a response versus fitted values plot
plot(pred.response(fit), y)
|
Loading required package: QUIC
d0 test.statistic pvalue
1 0 0.109842773 0.000
2 1 0.001617754 0.003
3 2 0.001565799 0.406
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