R: Multivariate normal additive models

mvn {mgcv} | R Documentation

## Multivariate normal additive models

### Description

Family for use with `gam` implementing smooth multivariate Gaussian regression. The means for each dimension are given by a separate linear predictor, which may contain smooth components. The Choleski factor of the response precision matrix is estimated as part of fitting.

### Usage

    mvn(d=2)

### Arguments

`d` | The dimension of the response (>1).

### Details

The response is `d` dimensional multivariate normal, where the covariance matrix is estimated, and the means for each dimension have sperate linear predictors. Model sepcification is via a list of gam like formulae - one for each dimension. See example.

Currently the family ignores any prior weights, and is implemented using first derivative information sufficient for BFGS estimation of smoothing parameters. `"response"` residuals give raw residuals, while `"deviance"` residuals are standardized to be approximately independent standard normal if all is well.

### Value

An object of class `general.family`.

### Author(s)

Simon N. Wood simon.wood@r-project.org

### See Also

`gaussian`

### Examples

    library(MASS)
    library(mgcv)
    ## simulate some data...
    V <- matrix(c(2,1,1,2),2,2)
    f0 <- function(x) 2 * sin(pi * x)
    f1 <- function(x) exp(2 * x)
    f2 <- function(x) 0.2 * x^11 * (10 * (1 - x))^6 + 10 *
                (10 * x)^3 * (1 - x)^10
    n <- 300
    x0 <- runif(n);x1 <- runif(n);
    x2 <- runif(n);x3 <- runif(n)
    y <- matrix(0,n,2)
    for (i in 1:n) {
      mu <- c(f0(x0[i])+f1(x1[i]),f2(x2[i]))
      y[i,] <- mvrnorm(1,mu,V)
    }
    dat <- data.frame(y0=y[,1],y1=y[,2],x0=x0,x1=x1,x2=x2,x3=x3)

    ## fit model...

    b <- gam(list(y0~s(x0)+s(x1),y1~s(x2)+s(x3)),family=mvn(d=2),data=dat)
    b
    summary(b)
    plot(b,pages=1)
    solve(crossprod(b$family$data$R)) ## estimated cov matrix

[Package mgcv version 1.8-3 Index]