StratigrapheR (version 1.2.4)

memento: Remembers and outputs the result of a slow function

Description

Memento mori; you do not have time to lose on unnecessary calculations. This function remembers the output of a slow function, for given arguments and, if asked politely, a given random seed. If they match the previous arguments and seeds, the output is provided without delay. The trade-off is to assign a folder to store the data.

Usage

memento(what, args, name, dir, subdir = "memento", check.seed = F, speak = T)

Arguments

what

a (slow) function

args

a list of the the arguments to give to the function. If they differ from saved values, the function will run again.

name

the name of the folder where to store the info. THIS NEEDS TO BE DIFFERENT FOR EACH IMPLEMENTATION OF THE FUNCTION IN IDENTICAL DIRECTORIES.

dir

the directory. You can set it as the working directory via getwd.

subdir

a name for a subdirectory (useful when the function is used several time in a script)

check.seed

if TRUE, the value of the random seed in effect will be taken into account; if it changes, the function will run again.

speak

whether to signify when the (slow) function is running

Value

the output of the function

Examples

# NOT RUN {
tf <- tempdir()

testfun <- function(a = 1, time = 3){

  Sys.sleep(time)

  return(a  + 0.1 * abs(rnorm(1)))

}

# First time running; the function takes some time, memento needs the
# output to be generated, and will remember for later.
set.seed(43)
memento(testfun,  args = list(a = 7), name = "T1", dir = tf)

set.seed(43)
testfun(7, time = 0)

# Second time running: memento directly outputs the remembered results.
# In this case, the seed is ignored, so the result is different from what
# would be obtained with a different seed
set.seed(45)
memento(testfun,  args = list(a = 7), name = "T1", dir = tf)

set.seed(45)
testfun(7, time = 0)

# First time running while taking into account the random seed;
# the function takes some time to generate the result
set.seed(42)
memento(testfun,  args = list(a = 7), name = "T1", dir = tf, check.seed = TRUE)

# Second time running with an identical random seed;
# memento directly outputs the results
set.seed(42)
memento(testfun,  args = list(a = 7), name = "T1", dir = tf, check.seed = TRUE)

# The seed is changed: the result is computed anew
set.seed(47)
memento(testfun,  args = list(a = 7), name = "T1", dir = tf, check.seed = TRUE)
# }
# NOT RUN {
# }