Hello Lou,

Thank you for making this package. I am having trouble forcing ata to use common items and the documentation is not clear on the usage. Here is an example: I want to use item 1,2,3 from the 100 item pool. However, none of these items actually appear on the final forms.

n_items <- 100
pool <- with(model_3pl_gendata(1, n_items), data.frame(id=1:n_items, a=a, b=b, c=c))
pool$content <- sample(1:3, n_items, replace=TRUE)
pool$time <- round(rlnorm(n_items, log(60), .2))
pool$group <- sort(sample(1:round(n_items/3), n_items, replace=TRUE))
pool$common <- c(rep(1,3),rep(0,97))

four 10-item forms to maximize b parameters

x <- ata(pool, 4, len=10, max_use=1)
x <- ata_obj_relative(x, 'b', 'max', negative=F)
x <- ata_item_fixedvalue(x,c(1,2,3), forms = 1)
x <- ata_item_fixedvalue(x,c(1,2,3), forms = 2)
x <- ata_item_fixedvalue(x,c(1,2,3), forms = 3)
x <- ata_item_fixedvalue(x,c(1,2,3), forms = 4)
x <- ata_solve(x, 'lpsolve')