الأخطاء والتحذيرات والرسائل في R

# Each condition type behaves differently
message('This is a message')
warning('This is a warning')
# stop() would halt here, so wrap it
tryCatch(stop('This is an error'), error = function(e) print(e))

divide <- function(x, y) {
  if (y == 0) stop('Division by zero is not allowed')
  x / y
}
tryCatch(divide(10, 0), error = function(e) cat('Error:', conditionMessage(e), '\n'))
divide(10, 2)

safe_sqrt <- function(x) {
  if (x < 0) {
    warning('Negative input; returning NaN')
    return(NaN)
  }
  sqrt(x)
}
result <- safe_sqrt(-4)
cat('Result:', result, '\n')

load_data <- function(n) {
  message('Loading ', n, ' records...')
  seq_len(n)
}
data <- suppressMessages(load_data(100))
cat('Got', length(data), 'records\n')

e <- simpleError('something went wrong')
w <- simpleWarning('this looks suspicious')
cat('Error class   :', class(e), '\n')
cat('Warning class :', class(w), '\n')
cat('Error message :', conditionMessage(e), '\n')
cat('Warning msg   :', conditionMessage(w), '\n')

tryCatch(
  log(-1),
  warning = function(w) {
    cat('Caught warning :', conditionMessage(w), '\n')
    cat('From call      :', deparse(conditionCall(w)), '\n')
  }
)

old_warn <- options(warn = 0)  # default: collect warnings
log(-1)  # just a warning
options(warn = 0)
tryCatch({
  options(warn = 2)
  log(-1)   # now fatal
}, error = function(e) cat('Caught as error:', conditionMessage(e), '\n'),
finally = options(old_warn))

# warn=1: print warnings immediately as they happen
old <- options(warn = 1)
result1 <- log(-1)
result2 <- sqrt(-4)
cat('Results:', result1, result2, '\n')
options(old)

# With warning: execution continues
f_warn <- function(x) { if (x < 0) warning('negative'); x^2 }
cat('warn result:', f_warn(-3), '\n')  # still computes 9

# With error: execution stops
f_stop <- function(x) { if (x < 0) stop('negative'); x^2 }
tryCatch(f_stop(-3), error = function(e) cat('stopped:', e$message, '\n'))

strict_log <- function(x) {
  withCallingHandlers(
    log(x),
    warning = function(w) {
      stop(paste('Strict mode: warning treated as error:', conditionMessage(w)))
    }
  )
}
tryCatch(strict_log(-1), error = function(e) cat('Error:', e$message, '\n'))
cat('log(4) =', strict_log(4), '\n')

# Without suppression: warning shown
result1 <- log(-1)
# With suppression: warning hidden
result2 <- suppressWarnings(log(-1))
cat('Both are NaN:', is.nan(result1), is.nan(result2), '\n')

# Summary of the three condition functions
tryCatch({
  message('Step 1 starting')
  warning('something looks odd')
  stop('cannot continue')
}, message = function(m) cat('MSG:', conditionMessage(m)),
   warning = function(w) cat('WARN:', conditionMessage(w), '\n'),
   error   = function(e) cat('ERR:', conditionMessage(e), '\n'))