assert_prob: Assert probability matrix or vector

In survdistr: Survival Distribution Container with Flexible Interpolation Methods

Assert probability matrix or vector

Description

Validates that the input is a proper probability matrix or vector representing either a survival function, cumulative distribution function (CDF), cumulative incidence function (CIF), discrete hazard, or discrete density.

Usage

assert_prob(x, times = NULL, type = "surv")

Arguments

x	(numeric() | matrix()) Survival vector or matrix (rows = observations, columns = time points).
times	(numeric() | NULL) Original time points. If NULL, extracted from names/colnames.
type	(character(1)) Type of probability function: "surv" (default), "cdf", "cif", "haz", or "dens".

Details

The following conditions must hold:

1. The input x is a numeric matrix with no missing values.

2. Time points (times) are numeric, non-negative, unique, and increasing. If not supplied, they are derived from ⁠(col)names(x)⁠ (coerced to numeric).

3. All values are valid probabilities, i.e. lie in [0,1].

4. Each row is monotone:

   • "surv": non-increasing survival curves, i.e. S(t_i) \ge S(t_{i+1}).

   • "cdf" / "cif": non-decreasing functions, i.e. F(t_i) \le F(t_{i+1}).

   • "haz" / "dens": no monotonicity requirement.

5. Boundary condition at t = 0:

   • "surv": S(0) = 1.

   • "cdf" / "cif": F(0) = 0.

   • "haz" / "dens": t_1 > 0 (otherwise, nonzero hazard/density at t = 0 implies S(0) \neq 1)

Value

Invisibly returns the validated numeric time points.

Examples

x = matrix(data = c(1, 0.6, 0.4,
                    0.8, 0.8, 0.7),
           nrow = 2, ncol = 3, byrow = TRUE)

# Explicitly provide time points
assert_prob(x, times = c(12, 34, 42), type = "surv")

# Or use column names as time points
colnames(x) = c(12, 34, 42)
assert_prob(x)

# check CDF
assert_prob(1 - x, type = "cdf")

# check discrete hazards
assert_prob(c(0.2, 0.01, 0.3), times = c(1, 2, 3), type = "haz")

# check discrete densities
assert_prob(c(0.2, 0.01, 0.3), times = c(1, 2, 3), type = "dens")

survdistr documentation built on April 9, 2026, 5:09 p.m.