hazard_rate: Network Hazard Rate

In srdyal/diffusiontest: Analysis of Diffusion and Contagion Processes on Networks

Network Hazard Rate

Description

The hazard rate is the instantaneous probability of adoption at each time representing the likelihood members will adopt at that time (Allison 1984). The shape of the hazard rate indicates the pattern of new adopters over time. Rapid diffusion with convex cumulative adoption curves will have hazard functions that peak early and decay over time whereas slow concave cumulative adoption curves will have hazard functions that are low early and rise over time. Smooth hazard curves indicate constant adoption whereas those that oscillate indicate variability in adoption behavior over time.

Usage

hazard_rate(obj, no.plot = FALSE, include.grid = TRUE, ...)

plot_hazard(x, ...)

## S3 method for class 'diffnet_hr'
plot(
  x,
  y = NULL,
  main = "Hazard Rate",
  xlab = "Time",
  ylab = "Hazard Rate",
  type = "b",
  include.grid = TRUE,
  bg = "lightblue",
  pch = 21,
  add = FALSE,
  ylim = c(0, 1),
  ...
)

Arguments

obj	A n\times T matrix (Cumulative adoption matrix obtained from toa_mat) or a diffnet object.
no.plot	Logical scalar. When TRUE, suppress plotting (only returns hazard rates).
include.grid	Logical scalar. When TRUE includes a grid on the plot.
...	further arguments to be passed to the method.
x	An object of class diffnet_hr.
y	ignored.
main	Character scalar. Title of the plot
xlab	Character scalar. x-axis label.
ylab	Character scalar. y-axis label.
type	Character scalar. See par.
bg	Character scalar. Color of the points.
pch	Integer scalar. See par.
add	Logical scalar. When TRUE it adds the hazard rate to the current plot.
ylim	Numeric vector. See plot.

Details

This function computes hazard rate, plots it and returns the hazard rate vector invisible (so is not printed on the console). For t>1, hazard rate is calculated as

\frac{q_t - q_{t-1}}{n - q_{t-1}}

where q_i is the number of adopters in time t, and n is the number of vertices in the graph.

In survival analysis, hazard rate is defined formally as

% \lambda(t)=\lim_{h\to +0}\frac{F(t+h)-F(t)}{h}\frac{1}{1-F(t)} %

Then, by approximating h=1, we can rewrite the equation as

% \lambda(t)=\frac{F(t+1)-F(t)}{1-F(t)} %

Furthermore, we can estimate F(t), the probability of not having adopted the innovation in time t, as the proportion of adopters in that time, this is F(t) \sim q_t/n, so now we have

% \lambda(t)=\frac{q_{t+1}/n-q_t/n}{1-q_t/n} = \frac{q_{t+1} - q_t}{n - q_t} %

As showed above.

The plot_hazard function is an alias for the plot.diffnet_hr method.

Value

A row vector of size T with hazard rates for t>1 of class diffnet_hr. The class of the object is only used by the S3 plot method.

Author(s)

George G. Vega Yon & Thomas W. Valente

References

Allison, P. (1984). Event history analysis regression for longitudinal event data. Beverly Hills: Sage Publications.

Wooldridge, J. M. (2010). Econometric Analysis of Cross Section and Panel Data (2nd ed.). Cambridge: MIT Press.

See Also

Other statistics: bass, classify_adopters(), cumulative_adopt_count(), dgr(), ego_variance(), exposure(), infection(), moran(), struct_equiv(), threshold(), vertex_covariate_dist()

Other visualizations: dgr(), diffusionMap(), drawColorKey(), grid_distribution(), plot_adopters(), plot_diffnet(), plot_diffnet2(), plot_infectsuscep(), plot_threshold(), rescale_vertex_igraph()

Examples

# Creating a random vector of times of adoption
toa <- sample(2000:2005, 20, TRUE)

# Computing cumulative adoption matrix
cumadopt <- toa_mat(toa)$cumadopt

# Visualizing the hazard rate
hazard_rate(cumadopt)

srdyal/diffusiontest documentation built on Dec. 9, 2024, 1:14 a.m.