cache {RbcBook1}R Documentation

cache an R expression to use the result without recomputation in later Sweave events

Description

cache an R expression to use the result without recomputation in later Sweave events

Usage

cache(name, expr)

Arguments

name character variable
expr R expression

Details

If the object tmp-[name].Rdata does not exist, expr is evaluated and written to tmp-[name].Rdata. Otherwise, tmp-[name].Rdata is loaded and assigned to [name].

Note that if a graph is produced as a side effect of the cached command, it will not be produced when the cached object is encountered in future weavings. To avoid this problem, explicitly create the graphics output so that it persists and can be reused on future weavings. In general this process should be avoided by making all graphical activities explicit, not byproducts of expensive calculations that are likely to be cached. In other words, all expensive calculations for which visualizations are of interest should return an object for which a plotting method is defined. The object calculation can be cached and the plotting method can be applied to the cached object.

Value

The value of expr.

Author(s)

Wolfgang Huber <w.huber@dkfz.heidelberg.de>

Examples

library(graph)
unix.time(cache("bigran", randomGraph(paste("a", 1:100), 1:20, .3)))
dir()
unix.time(cache("bigran", randomGraph(paste("a", 1:100), 1:20, .3)))

[Package RbcBook1 version 1.0.2 Index]