ahaz.partial {ahaz} R Documentation

## Partial calculation of estimating quantities used by ahaz

### Description

Partial calculation of the quantities used in the estimating equations for ahaz.

### Usage

```ahaz.partial(surv, X, weights, idx)
```

### Arguments

 `surv` Response in the form of a survival object, as returned by the function `Surv()` in the package survival. Right-censored and counting process format (left-truncation) is supported. Tied survival times are not supported. `X` Design matrix. Missing values are not supported. `weights` Optional vector of observation weights. Default is 1 for each observation. `idx` Vector of indices of covariates to use in the calculations.

### Details

The function is intended mainly for programming use when a very large number of covariates are considered and direct application of `ahaz` is unfeasible.

The estimating equations for the semiparametric additive hazards model are of the form D*beta=d with D a quadratic matrix with number of columns equal to the number of covariates. The present function returns `d[idx]`, `D[idx,]`, and `B[idx,]`; the latter a matrix such that D^{-1} B D^{-1} estimates the covariance matrix of the regression coefficients.

### Value

A list containing the following elements:

 `call` The call that produced this object. `idx` A copy of the argument `idx`. `nobs` Number of observations. `nvars` Number of covariates. `d` Vector of length `length(idx)`. `D` Matrix of size `length(idx) x nvars`. `B` Matrix of size `length(idx) x nvars`.

`ahaz`, `ahaz.adjust`.

### Examples

```data(sorlie)

# Break ties
set.seed(10101)
time <- sorlie\$time+runif(nrow(sorlie))*1e-2

# Survival data + covariates
surv <- Surv(time,sorlie\$status)
X <- as.matrix(sorlie[,3:ncol(sorlie)])

# Get D for the first 10 covariates only
a<-ahaz.partial(surv,X,idx=1:10)
pD1 <- a\$D

# Equivalent to the (slower) solution
b <- ahaz(surv,X)
pD2 <- b\$D[1:10,]
max(abs(pD1-pD2))

```

[Package ahaz version 1.14 Index]