% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/pspaceDecay.R
\name{linearDecay}
\alias{linearDecay}
\title{Constructor of linear decay functions}
\usage{
linearDecay(decay = 0.001, pdist = 0.15, plot = FALSE, demo.signal = 1)
}
\arguments{
\item{decay}{A decay factor (in [0,1]). This term indicates how much a
\code{signal} decreases as a function of distance in pathway space. 
For example, at a specific distance defined by the \code{pdist} parameter, 
the signal intensity will be the initial signal multiplied by \code{decay}.}

\item{pdist}{A distance normalization term (in (0, 1]) at which the signal 
reaches `signal * decay`. This parameter is used to anchor the decay to 
a meaningful distance (see `details`). Also, when \code{pdist = 1}, it will
represent the diameter of the inscribed circle within the coordinate space
of a `PathwaySpace` object.}

\item{plot}{A logical value indicating whether to return a `ggplot` object.}

\item{demo.signal}{A numeric value in `[-Inf, Inf]`, only passed when 
\code{plot = TRUE} to visualize the decay curve with a specific signal 
intensity. The value is ignored by the function constructor, as the decay 
function itself is returned without using an initial signal.}
}
\value{
Returns either a function of the form 
\code{function(x, signal) \{ ... \}} or, if \code{plot = TRUE}, a `ggplot`
object illustrating the decay model.
}
\description{
The `linearDecay()` constructor either creates a decay function or 
returns a `ggplot` object for visualizing the decay model. It is a utility 
function used internally by \code{\link{circularProjection}} and 
\code{\link{polarProjection}}.
}
\details{
The `linearDecay()` constructor creates a simple linear decay model. It 
describes how a signal decreases proportionally with distance.

The decay function is defined as:
\deqn{y = signal \times \left(1 - (1 - decay) \times \frac{x}{pdist}\right)}

where \eqn{signal} represents the initial intensity, \eqn{decay} defines 
the relative signal level at \eqn{pdist}, and \eqn{x} is a vector of 
normalized distances. The signal decreases uniformly from its initial 
value to \eqn{pdist}, which is a reference distance that anchors 
the model such that:
\itemize{
  \item \eqn{y = signal} when \eqn{x = 0}
  \item \eqn{y = signal \times decay} when \eqn{x = pdist}
}

This makes the linear form consistent with the exponential and Weibull decay
functions, both of which also reach \eqn{signal \times decay} at the
reference distance.
}
\examples{
# Return a decay function
decay_fun <- linearDecay(decay = 0.5, pdist = 0.25)

# Plot decay model parameters
# linearDecay(decay = 0.5, pdist = 0.25, plot = TRUE)

}
\seealso{
\code{\link{expDecay}}, \code{\link{weibullDecay}}
}
\author{
Sysbiolab Team
}
