# An R package for simulating and plotting quantities of interest from Cox Proportional Hazard models.

### Description

An R package for simulating and plotting quantities of interest (relative hazards, first differences, and hazard ratios) for linear coefficients, multiplicative interactions, polynomials, penalised splines, and non-proportional hazards, as well as stratified survival curves from Cox Proportional Hazard models.

The package includes the following simulation functions:

`coxsimLinear`

: a function for simulating relative hazards, first differences, hazard ratios, and hazard rates for linear, non-time interacted covariates from Cox Proportional Hazard (`coxph`

) models.`coxsimtvc`

: a function for simulating time-interactive hazards (relative hazards, first differences, and hazard ratios) for covariates from Cox Proportional Hazard models. The function will calculate time-interactive hazard ratios for multiple strata estimated from a stratified Cox Proportional Hazard model.`coxsimSpline`

: a function for simulating quantities of interest from penalised splines using multivariate normal distributions. Currently does not support simulating hazard rates from stratified models. Note: be extremely careful about the number of simulations you ask the function to find. It is very easy to ask for more than your computer can handle.`coxsimPoly`

: a function for simulating quantities of interest for a range of values for a polynomial nonlinear effect from Cox Proportional Hazard models.`coxsimInteract`

: a function for simulating quantities of interest for linear multiplicative interactions, including marginal effects and hazard rates.

Results from these functions can be plotted using the `simGG`

method.

The package also includes two functions that make it easier to create time interactions:

`SurvExpand`

: a function to convert a data frame of non-equal interval continuous observations into equal interval continuous observations.`tvc`

: a function to create time interaction variables that can be used in a`coxph`

model (or any other model with time interactions).setXl: a function for setting valid

`Xl`

values given a sequence of fitted`Xj`

values. This makes it more intituitive to find hazard ratios and first differences for comparisons between some*Xj*fitted values and*Xl*values other than 0.

### References

Gandrud, Christopher. 2015. simPH: An R Package for Illustrating Estimates from Cox Proportional Hazard Models Including for Interactive and Nonlinear Effects. Journal of Statistical Software. 65(3)1-20.