MCI (version 1.3.3)

model.fit: Goodness of fit statistics for the Huff model

Description

This function calculates several goodness of fit values to evaluate how good the observed values fit the empirical observations.

Usage

model.fit(y_obs, y_exp, plotVal = FALSE)

Arguments

y_obs

Observed values of the dependent variable \(y\)

y_exp

Expected values of the dependent variable \(y\) (model results)

plotVal

Logical argument that indicates if the function plots a graph comparing observed and expected values

Value

list:

resids_sq_sum

Sum of squared residuals

pseudorsq

Pseudo-R-squared

globerr

Global error

mape

Mean average percentage error

Details

This function computes several goodness of fit statistics to evaluate the results of non-linear fitting procedures for the Huff model (see the functions huff.attrac and huff.fit). Besides the sum of squared residuals, the function also calculates a Pseudo-R-squared measure and the MAPE (mean average percentage error), both used by De Beule et al. (2014), and the global error used by Klein (1988).

References

De Beule, M./Van den Poel, D./Van de Weghe, N. (2014): “An extended Huff-model for robustly benchmarking and predicting retail network performance”. In: Applied Geography, 46, 1, p. 80-89.

Klein, R. (1988): “Der Lebensmittel-Einzelhandel im Raum Verden. Raeumliches Einkaufsverhalten unter sich wandelnden Bedingungen”. Flensburger Arbeitspapiere zur Landeskunde und Raumordnung, 6. Flensburg.

See Also

huff.fit

Examples

# NOT RUN {
# Controlling the fit of a Huff Model market area estimation #

data(Freiburg1)
data(Freiburg2)
data(Freiburg3)
# Loads the data

huff_mat <- huff.shares (Freiburg1, "district", "store", "salesarea", "distance")
# Market area estimation using the Huff Model with standard parameters
# (gamma = 1, lambda = -2)

huff_mat_pp <- merge (huff_mat, Freiburg2)
# Adding the purchasing power data for the city districts

huff_total <- shares.total (huff_mat_pp, "district", "store", "p_ij", "ppower")
# Total expected sales and shares

huff_total_control <- merge (huff_total, Freiburg3, by.x = "suppliers_single",
by.y = "store")

model.fit(huff_total_control$annualsales, huff_total_control$sum_E_j, plotVal = TRUE)
# Observed vs. expected

# Results can be adressed directly:
huff_fit <- model.fit(huff_total_control$annualsales, huff_total_control$sum_E_j, plotVal = TRUE)
huff_fit$mape
# }