logger (version 0.4.0)

log_eval: Evaluate an expression and log results

Description

Evaluate an expression and log results

Usage

log_eval(expr, level = TRACE, multiline = FALSE)

Arguments

expr

R expression to be evaluated while logging the expression itself along with the result

level

log_levels()

multiline

setting to FALSE will print both the expression (enforced to be on one line by removing line-breaks if any) and its result on a single line separated by =>, while setting to TRUE will log the expression and the result in separate sections reserving line-breaks and rendering the printed results

Examples

old <- logger:::namespaces_set()
log_eval(pi * 2, level = INFO)

## lowering the log level threshold so that we don't have to set a higher level in log_eval
log_threshold(TRACE)
log_eval(x <- 4)
log_eval(sqrt(x))

## log_eval can be called in-line as well as returning the return value of the expression
x <- log_eval(mean(runif(1e3)))
x

## https://twitter.com/krlmlr/status/1067864829547999232
f <- sqrt
g <- mean
x <- 1:31
log_eval(f(g(x)), level = INFO)
log_eval(y <- f(g(x)), level = INFO)

## returning a function
log_eval(f <- sqrt)
log_eval(f)

## evaluating something returning a wall of "text"
log_eval(f <- log_eval)
log_eval(f <- log_eval, multiline = TRUE)

## doing something computationally intensive
log_eval(system.time(for (i in 1:100) mad(runif(1000))), multiline = TRUE)
logger:::namespaces_set(old)