comp_min_N computes a population size value N (an integer
as a power of 10) so that the frequencies of the 4 combinations of conditions and decisions
(i.e., the cells of the confusion table, or center row of boxes in the frequency prism)
reach or exceed a minimum value min_freq given the basic parameters
prev, sens, and spec (spec = 1 - fart).
Arguments
- prev
The condition's prevalence value
prev(i.e., the probability of condition being TRUE).- sens
The decision's sensitivity value
sens(i.e., the conditional probability of a positive decision provided that the condition is TRUE).- spec
The specificity value
spec(i.e., the conditional probability of a negative decision provided that the condition is FALSE).- min_freq
The minimum frequency of each combination of a condition and a decision (i.e., hits, misses, false alarms, and correct rejections). Default:
min_freq = 1.
Value
An integer value N (as a power of 10).
Details
Using this function helps avoiding excessively small decimal values in categories
– especially hi, mi, fa, cr –
when expressing combinations of conditions and decisions as natural frequencies.
As values of zero (0) are tolerable, the function only increases N
(in powers of 10) while the current value of any frequency (cell in confusion table or
leaf of a frequency tree) is positive but below min_freq.
By default, comp_freq_prob and comp_freq
round frequencies to nearest integers to avoid decimal values in
freq (i.e., round = TRUE by default).
Using the option round = FALSE turns off rounding.
See also
population size N;
num contains basic numeric parameters;
freq contains current frequency information;
comp_freq computes frequencies from probabilities;
prob contains current probability information;
comp_prob computes probabilities from probabilities;
comp_freq_freq computes current frequency information from (4 essential) frequencies;
comp_freq_prob computes current frequency information from (3 essential) probabilities;
comp_prob_freq computes current probability information from (4 essential) frequencies;
comp_prob_prob computes current probability information from (3 essential) probabilities.
Other functions computing frequencies:
comp_freq(),
comp_freq_freq(),
comp_freq_prob(),
comp_prob_prob()
Examples
comp_min_N(0, 0, 0) # => 1
#> Warning: Extreme case (prev = 0 & spec = 0):
#> N fa (FP) cases; 0 cond_true or dec_true cases; PPV = NaN.
#> [1] 1
comp_min_N(1, 1, 1) # => 1
#> Warning: Extreme case (prev = 1 & sens = 1):
#> N hi (TP) cases; 0 cond_false or dec_false cases; NPV = NaN.
#> [1] 1
comp_min_N(1, 1, 1, min_freq = 10) # => 10
#> Warning: Extreme case (prev = 1 & sens = 1):
#> N hi (TP) cases; 0 cond_false or dec_false cases; NPV = NaN.
#> [1] 10
comp_min_N(1, 1, 1, min_freq = 99) # => 100
#> Warning: Extreme case (prev = 1 & sens = 1):
#> N hi (TP) cases; 0 cond_false or dec_false cases; NPV = NaN.
#> [1] 100
comp_min_N(.1, .1, .1) # => 100 = 10^2
#> [1] 100
comp_min_N(.001, .1, .1) # => 10 000 = 10^4
#> [1] 10000
comp_min_N(.001, .001, .1) # => 1 000 000 = 10^6
#> [1] 1e+06
comp_min_N(.001, .001, .001) # => 1 000 000 = 10^6
#> [1] 1e+06