Implement conditional statistics

[smith-garrett]

CDF/quantile fns. need to know which transient states exit into which absorbing states in order to implement for systems with more than one absorbing state.

CDF_abs = 1 - (sum_{transient states exiting into abs} / splitting probability_abs)

[smith-garrett]

Also need to be implemented:

• mean(fp, dims=...)
• var(fp, dims=...)

[smith-garrett]

cond_mean(d::fpdistribution) = -(d.A * d.T^-2 * d.p0) ./ (d.A * inv(d.T) * d.p0)

[smith-garrett]

One way of calculating cond. CDF: condcdf(fp, t) = fp.A * (exp(t*fp.T) - I) * inv(fp.T) * p0, Lindquist (2022)