get_obs_dens {geocausal}

Generate observed densities

Description

'get_obs_dens()' takes a hyperframe and returns observed densities. The output is used as propensity scores.

Usage

get_obs_dens(hfr, dep_var, indep_var, ngrid = 100, window)

Arguments

hfr

hyperframe

dep_var

The name of the dependent variable. Since we need to obtain the observed density of treatment events, 'dep_var' should be the name of the treatment variable.

indep_var

vector of names of independent variables (covariates)

ngrid

the number of grid cells that is used to generate observed densities. By default = 100. Notice that as you increase 'ngrid', the process gets computationally demanding.

window

owin object

Details

'get_obs_dens()' assumes the poisson point process model and calculates observed densities for each time period. It depends on 'spatstat.model::mppm()'. Users should note that the coefficients in the output are not directly interpretable, since they are the coefficients inside the exponential of the poisson model.

Value

list of the following: * 'indep_var': independent variables * 'coef': coefficients * 'intens_grid_cells': im object of observed densities for each time period * 'estimated_counts': the number of events that is estimated by the poisson point process model for each time period * 'sum_log_intens': the sum of log intensities for each time period

Examples

# Data
dat_out <- insurgencies[1:100, ]
dat_out$time <- as.numeric(dat_out$date - min(dat_out$date) + 1)

# Hyperframe
dat_hfr <- get_hfr(data = dat_out,
                   col = "type",
                   window = iraq_window,
                   time_col = "time",
                   time_range = c(1, max(dat_out$time)),
                   coordinates = c("longitude", "latitude"),
                   combine = TRUE)

# Covariates
dist_baghdad <- get_dist_focus(window = iraq_window,
                               lon = c(44.366), #Baghdad
                               lat = c(33.315),
                               resolution = 0.1,
                               mile = FALSE,
                               preprocess = FALSE)

dat_hfr$dist_bagh <- dist_baghdad

# Observed density
get_obs_dens(dat_hfr,
             dep_var = "all_combined",
             indep_var = c("dist_bagh"),
             ngrid = 100,
             window = iraq_window)