Single-line timing

A common way to time a line of R code is to save Sys.time() to a variable before the code you want to evaluate, and then find the difference of Sys.time() after. This will have R output text something along the lines of Time difference of 5.335534 secs

However, if you are running a script that has multiple of these timings, the printed results are not useful. A hack would be to do a print() statement before the time difference calculation, but that just looks ugly, especially in knitr documents.

Below is a function that will take a string of what you are timing, and the difftime calculation, and cats back a nice prompt for you.

print_difftime_prompt <- function(str_what_did_you_time, diff_time, sep=':'){
    parse_time <- unclass(diff_time)[1]
    parse_units <- attr(unclass(diff_time), 'units')
    prompt_string <- sprintf('%s took: %s %s', str_what_did_you_time, parse_time, parse_units)
    cat(prompt_string, '\n')
    # return(prompt_string)
}

For example: strt <- Sys.time() print_difftime_prompt(‘add simulation dataframes to list’, Sys.time() - strt) will return: add simulation dataframes to list took: 36.1213629245758 secs

Microbenchmark

Additionally, do get an accurate time, use the microbenchmark() function in the microbenchmark package. See Hadley’s post about it’s use.