Compute the Gini coefficient
Hello,
Thank you very much for your help.
How can I draw a Lorenz curve with several replications ?
Here is an example with 4 replications:
hosts=c(23,31,19,10,7,7,3,
39,40,8,3,6,2,2,
47,17,8,10,6,11,1,
30,30,10,0,15,15,0)
parasites=rep(seq(from=0,to=6,by=1),4)
replications=c(rep(1,7),rep(2,7),rep(3,7),rep(4,7))
test <- cbind(parasites,hosts,replications)
Should I calculate the average frequency of hosts (replication mean values) and next calculate the cumulative percentage of hosts from the average frequency ?
Thank you very much for your time.
Have a nice day.
Marine
________________________________________
De : Achim Zeileis <Achim.Zeileis at uibk.ac.at>
Envoy? : mercredi 30 mars 2016 12:05
? : Erich Neuwirth
Cc : Marine Regis; r-help at r-project.org
Objet : Re: [R] Compute the Gini coefficient
On Wed, 30 Mar 2016, Erich Neuwirth wrote:
On 30 Mar 2016, at 02:53, Marine Regis <marine.regis at hotmail.fr> wrote: Hello, I would like to build a Lorenz curve and calculate a Gini coefficient in order to find how much parasites does the top 20% most infected hosts support. Here is my data set: Number of parasites per host: parasites = c(0,1,2,3,4,5,6,7,8,9,10) Number of hosts associated with each number of parasites given above: hosts = c(18,20,28,19,16,10,3,1,0,0,0) To represent the Lorenz curve: I manually calculated the cumulative percentage of parasites and hosts: cumul_parasites <- cumsum(parasites)/max(cumsum(parasites)) cumul_hosts <- cumsum(hosts)/max(cumsum(hosts)) plot(cumul_hosts, cumul_parasites, type= "l?)
Your values in hosts are frequencies. So you need to calculate cumul_hosts = cumsum(hosts)/sum(hosts) cumul_parasites = cumsum(hosts*parasites)/sum(parasites)
That's what I thought as well but Marine explicitly said that the 'host' are _not_ weights. Hence I was confused what this would actually mean. Using the "ineq" package you can also do plot(Lc(parasites, hosts))
The Lorenz curves starts at (0,0), so to draw it, you need to extend these vectors cumul_hosts = c(0,cumul_hosts) cumul_parasites = c(0,cumul_parasites) plot(cumul_hosts,cum9l_parasites,type=?l?) The Gini coefficient can be calculated as library(reldist) gini(parasites,hosts) If you want to check, you can ?recreate? the original data (number of parasited for each host) with num_parasites = rep(parasites,hosts) and gini(num_parasites) will also give you the Gini coefficient you want.
From this Lorenz curve, how can I calculate the Gini coefficient with the function "gini" in R (package reldist) given that the vector "hosts" is not a vector of weights ?
Thank you very much for your help.
Have a nice day
Marine
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