# Function to compute the abundance of new or old RNA at time t for non-constant rates.

Source:`R/modeling.R`

`f.nonconst.Rd`

The standard mass action kinetics model of gene expression arises from the differential equation \(df/dt = s(t) - d(t) f(t)\), with s(t) being the synthesis rate at time t, d(t) the degradation rate at time t and \(f0=f(0)\) (the abundance at time 0). Here, both s and d have the following form \(s(t)=so+sf \cdot t^{se}\).

## Arguments

- t
time in h (can be a vector)

- f0
the abundance at time t=0

- s
the synthesis rate (see details)

- d
the degradation rate (see details)

## Details

Both rates can be either (i) a single number (constant rate), (ii) a data frame with names "offset", "factor" and "exponent" (for linear functions, see ComputeNonConstantParam; only one row allowed) or (iii) a unary function time->rate. Functions