# Coxme variance function

### Description

This variance function accepts a list of matrices, which define a correlation structure for a coxme fit.

### Usage

1 | ```
coxmeMlist(varlist, rescale = FALSE, pdcheck = TRUE, positive = TRUE)
``` |

### Arguments

`varlist` |
a list containing one or more matrix or bdsmatrix objects. |

`rescale` |
if TRUE, each input matrix is rescaled to have a diagonal of 1. (Kinship matrices for instance are often generated with a diagonal of .5 and would be multiplied by 2). |

`pdcheck` |
check each matrix to ensure that it is positive definite |

`positive` |
constrain coefficients to be positive. This may also be a vector of
the same length as |

### Details

If two matrices *A* and *B* were given, this fits
the variance structure
*V = s1 A + s2 B*,
where the variances *s1* and *s2* are
parameters that will be optimized by `coxme`

,
treating *A* and *B* as fixed.

### Value

a coxme variance family object, used by `coxme`

in the fitting process.

### Author(s)

Terry Therneau

### See Also

`coxme`