comp_PPV {riskyr}

Compute a decision's positive predictive value (PPV) from probabilities.

Description

comp_PPV computes the positive predictive value PPV from 3 essential probabilities prev, sens, and spec.

Usage

comp_PPV(prev, sens, spec)

Arguments

prev

The condition's prevalence prev (i.e., the probability of condition being TRUE).

sens

The decision's sensitivity sens (i.e., the conditional probability of a positive decision provided that the condition is TRUE).

spec

The decision's specificity value spec (i.e., the conditional probability of a negative decision provided that the condition is FALSE).

Details

comp_PPV uses probabilities (not frequencies) and does not round results.

Value

The positive predictive value PPV as a probability. A warning is provided for NaN values.

See Also

comp_sens and comp_NPV compute related probabilities; is_extreme_prob_set verifies extreme cases; comp_complement computes a probability's complement; is_complement verifies probability complements; comp_prob computes current probability information; prob contains current probability information; is_prob verifies probabilities.

Other functions computing probabilities: comp_FDR(), comp_FOR(), comp_NPV(), comp_accu_freq(), comp_accu_prob(), comp_acc(), comp_comp_pair(), comp_complement(), comp_complete_prob_set(), comp_err(), comp_fart(), comp_mirt(), comp_ppod(), comp_prob_freq(), comp_prob(), comp_sens(), comp_spec()

Examples

# (1) Ways to work:
comp_PPV(.50, .500, .500)  # => PPV = 0.5
comp_PPV(.50, .333, .666)  # => PPV = 0.499

# (2) Watch out for vectors:
prev <- seq(0, 1, .1)
comp_PPV(prev, .5, .5)  # => without NaN values
comp_PPV(prev,  0,  1)  # => with NaN values

# (3) Watch out for extreme values:
comp_PPV(prev = 1, sens = 0, spec = .5)  # => NaN, only mi: hi = 0 and fa = 0: PPV = 0/0 = NaN
is_extreme_prob_set(prev = 1, sens = 0, spec = .5)  # => verifies extreme cases

comp_PPV(prev = 0, sens = .5, spec = 1)  # => NaN, only cr: hi = 0 and fa = 0: PPV = 0/0 = NaN
is_extreme_prob_set(prev = 0, sens = .5, spec = 1)  # => verifies extreme cases

comp_PPV(prev = .5, sens = 0, spec = 1)  # => NaN, only cr: hi = 0 and fa = 0: PPV = 0/0 = NaN
is_extreme_prob_set(prev = .5, sens = 0, spec = 1)  # => verifies extreme cases