init_num initializes basic numeric variables to define num as a list of named elements containing four basic probabilities (prev, sens, spec, and fart) and one frequency parameter (the population size N).

init_num(prev = num.def$prev, sens = num.def$sens,
spec = num.def$spec, fart = num.def$fart, N = num.def$N) ## Arguments prev The condition's prevalence value prev (i.e., the probability of condition being TRUE). The decision's sensitivity value sens (i.e., the conditional probability of a positive decision provided that the condition is TRUE). The decision's specificity value spec (i.e., the conditional probability of a negative decision provided that the condition is FALSE). spec is optional when is complement fart is provided. The decision's false alarm rate fart (i.e., the conditional probability of a positive decision provided that the condition is FALSE). fart is optional when its complement spec is provided. The population size N. ## Value A list containing a valid quadruple of probabilities (prev, sens, spec, and fart) and one frequency (population size N). ## Details If spec is provided, its complement fart is optional. If fart is provided, its complement spec is optional. If no N is provided, a suitable minimum value is computed by comp_min_N. ## See also num contains basic numeric parameters; pal contains current color settings; txt contains current text settings; freq contains current frequency information; comp_freq computes frequencies from probabilities; prob contains current probability information; comp_prob computes current probability information; is_valid_prob_set verifies sets of probability inputs; is_extreme_prob_set verifies sets of extreme probabilities; comp_min_N computes a suitable minimum population size N. Other functions initializing scenario information: init_pal, init_txt, riskyr ## Examples # ways to succeed: init_num(1, 1, 1, 0, 100) # => succeeds#> Warning: Extreme case (prev = 1 & sens = 1): #> N hi (TP) cases; 0 cond_false or dec_false cases; NPV = NaN.#>$prev
#> [1] 1
#>
#> $sens #> [1] 1 #> #>$spec
#> [1] 1
#>
#> $fart #> [1] 0 #> #>$N
#> [1] 100
#> init_num(1, 1, 0, 1, 100)  # => succeeds#> Warning: Extreme case (prev = 1 & sens = 1):
#>   N hi (TP) cases; 0 cond_false or dec_false cases; NPV = NaN.#> $prev #> [1] 1 #> #>$sens
#> [1] 1
#>
#> $spec #> [1] 0 #> #>$fart
#> [1] 1
#>
#> $N #> [1] 100 #> # watch out for: init_num(1, 1, 0, 1) # => succeeds (with N computed)#> Warning: Extreme case (prev = 1 & sens = 1): #> N hi (TP) cases; 0 cond_false or dec_false cases; NPV = NaN.#>$prev
#> [1] 1
#>
#> $sens #> [1] 1 #> #>$spec
#> [1] 0
#>
#> $fart #> [1] 1 #> #>$N
#> [1] 1000
#> init_num(1, 1, NA, 1, 100)     # => succeeds (with spec computed)#> Warning: Extreme case (prev = 1 & sens = 1):
#>   N hi (TP) cases; 0 cond_false or dec_false cases; NPV = NaN.#> $prev #> [1] 1 #> #>$sens
#> [1] 1
#>
#> $spec #> [1] 0 #> #>$fart
#> [1] 1
#>
#> $N #> [1] 100 #> init_num(1, 1, 0, NA, 100) # => succeeds (with fart computed)#> Warning: Extreme case (prev = 1 & sens = 1): #> N hi (TP) cases; 0 cond_false or dec_false cases; NPV = NaN.#>$prev
#> [1] 1
#>
#> $sens #> [1] 1 #> #>$spec
#> [1] 0
#>
#> $fart #> [1] 1 #> #>$N
#> [1] 100
#> init_num(1, 1, NA, 1)          # => succeeds (with spec and N computed)#> Warning: Extreme case (prev = 1 & sens = 1):
#>   N hi (TP) cases; 0 cond_false or dec_false cases; NPV = NaN.#> $prev #> [1] 1 #> #>$sens
#> [1] 1
#>
#> $spec #> [1] 0 #> #>$fart
#> [1] 1
#>
#> $N #> [1] 1000 #> init_num(1, 1, 0, NA) # => succeeds (with fart and N computed)#> Warning: Extreme case (prev = 1 & sens = 1): #> N hi (TP) cases; 0 cond_false or dec_false cases; NPV = NaN.#>$prev
#> [1] 1
#>
#> $sens #> [1] 1 #> #>$spec
#> [1] 0
#>
#> $fart #> [1] 1 #> #>$N
#> [1] 1000
#> init_num(1, 1, .51, .50, 100)  # => succeeds (as spec and fart are within tolarated range)#> Warning: Extreme case (prev = 1 & sens = 1):
#>   N hi (TP) cases; 0 cond_false or dec_false cases; NPV = NaN.#> $prev #> [1] 1 #> #>$sens
#> [1] 1
#>
#> $spec #> [1] 0.51 #> #>$fart
#> [1] 0.5
#>
#> $N #> [1] 100 #> # ways to fail: init_num(prev = NA) # => NAs + warning (NA)#>$prev
#> [1] NA
#>
#> $sens #> [1] NA #> #>$spec
#> [1] NA
#>
#> $fart #> [1] NA #> #>$N
#> [1] NA
#> init_num(prev = 88)                                  # => NAs + warning (beyond range)#> $prev #> [1] NA #> #>$sens
#> [1] NA
#>
#> $spec #> [1] NA #> #>$fart
#> [1] NA
#>
#> $N #> [1] NA #> init_num(prev = 1, sens = NA) # => NAs + warning (NA)#>$prev
#> [1] NA
#>
#> $sens #> [1] NA #> #>$spec
#> [1] NA
#>
#> $fart #> [1] NA #> #>$N
#> [1] NA
#> init_num(prev =  1, sens = 1, spec = NA, fart = NA)  # => NAs + warning (NAs)#> $prev #> [1] NA #> #>$sens
#> [1] NA
#>
#> $spec #> [1] NA #> #>$fart
#> [1] NA
#>
#> $N #> [1] NA #> init_num(1, 1, .52, .50, 100) # => NAs + warning (complements beyond range)#> Warning: Probabilities (p1 and p2) are not complements (in tolerated range).#>$prev
#> [1] NA
#>
#> $sens #> [1] NA #> #>$spec
#> [1] NA
#>
#> $fart #> [1] NA #> #>$N
#> [1] NA
#>