I would like to calculate the gini coefficient of several plots with R unsing the gini() function from the package reldist.
I have a data frame from which I need to use two columns as input to the gini function.
> head(merged[,c(1,17,29)])
idp c13 w
1 19 126 14.14
2 19 146 14.14
3 19 76 39.29
4 19 74 39.29
5 19 86 39.29
6 19 93 39.29
The gini function uses the first elements for calculation (c13 here) and the second elements are the weights (w here) corresponding to each element from c13.
So I need to use the column c13 and w like this:
gini(merged$c13,merged$w)
[1] 0.2959369
The thing is I want to do this for each plot (idp). I have 4 thousands different values of idp with dozens of values of the two other columns for each.
I thought I could do this using the function tapply(). But I can't put two colums in the function using tapply.
tapply(list(merged$c13,merged$w), merged$idp, gini)
As you know this does not work.
So what I would love to get as a result is a data frame like this:
idp Gini
1 19 0.12
2 21 0.45
3 35 0.65
4 65 0.23
Do you have any idea of how to do this?? Maybe the plyr package?
Thank you for your help!