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Background

Povcalnet uses two methods to estimate poverty and inequality statistics from grouped data.
* One method is based on fitting a Lorenz Quadratic functional form to the grouped data
* the other one uses a Beta Lorenz function

This vignette focuses on the Lorenz Quadratic method.

High level example

# Input definition
welfare_mean    <- 51.56
ppp             <- 3.69
daily_povline   <- 1.9
monthly_povline <- daily_povline * 365 / 12

# Create grouped data (Type 1)
# http://iresearch.worldbank.org/povcalnet/PovCalculator.aspx
population <- c(0.0005,
                0.0032,
                0.014799999999999999,
                0.0443,
                0.0991,
                0.257,
                0.4385,
                0.5938,
                0.7089,
                1)

welfare <- c(5.824760527229386e-05,
             0.000604029410841011,
             0.0037949334793616948,
             0.013988878652244477,
             0.036992164583098786,
             0.12140708906131342,
             0.24531391873082081,
             0.37446670169288321,
             0.48753116241194566,
             1)


# Estimate poverty statistics
wbpip:::gd_compute_pip_stats_lq(welfare         = welfare,
                        population      = population,
                        requested_mean  = welfare_mean,
                        povline         = monthly_povline,
                        default_ppp     = ppp)
#> $mean
#> [1] 51.56
#> 
#> $poverty_line
#> [1] 57.79167
#> 
#> $z_min
#> [1] 19.32239
#> 
#> $z_max
#> [1] 130.4877
#> 
#> $ppp
#> [1] 3.69
#> 
#> $gini
#> [1] 0.3212646
#> 
#> $median
#> [1] 42.24282
#> 
#> $rmhalf
#> [1] 30.3349
#> 
#> $polarization
#> [1] 0.2206622
#> 
#> $ris
#> [1] 0.2941709
#> 
#> $mld
#> [1] 0.1897891
#> 
#> $dcm
#> [1] 34.9956
#> 
#> $deciles
#>  [1] 0.03745935 0.05010249 0.06009842 0.06896129 0.07754930 0.08659087
#>  [7] 0.09703444 0.11071236 0.13305853 0.27843295
#> 
#> $headcount
#> [1] 0.7601359
#> 
#> $poverty_gap
#> [1] 0.2762329
#> 
#> $poverty_severity
#> [1] 0.1283636
#> 
#> $eh
#> [1] -0.8715094
#> 
#> $epg
#> [1] -1.751794
#> 
#> $ep
#> [1] -2.303913
#> 
#> $gh
#> [1] -0.09397473
#> 
#> $gpg
#> [1] 0.7032745
#> 
#> $gp
#> [1] 1.53591
#> 
#> $watts
#> [1] 0.3909738
#> 
#> $dl
#> [1] 1.120862
#> 
#> $ddl
#> [1] 1.691956
#> 
#> $is_normal
#> [1] TRUE
#> 
#> $is_valid
#> [1] TRUE
#> 
#> $sse
#> [1] 0.003221566
#> 
#> $ssez
#> [1] 0.003221566
#> 
#> $ymean
#> [1] 0.09219419
#> 
#> $sst
#> [1] 0.08792027
#> 
#> $coef
#> [1]  0.7959815 -1.4445934  0.1472819
#> 
#> $sse
#> [1] 8.003335e-07
#> 
#> $r2
#> [1] 0.9999909
#> 
#> $mse
#> [1] 1.333889e-07
#> 
#> $se
#> [1] 0.00550664 0.02284612 0.01526564