ata_helpers: Helper functions of ATA
In xxIRT: Item Response Theory and Computer-Based Testing in R

miscellaneous helper functions of ATA

ata_append_constraints appends constraint definitions to the model

ata_form_index converts input forms into actual form indices in the model

ata_obj_coef processes input coefficients of the objective functions

ata_solve_lpsolve solves the the MIP model using lp_solve

ata_solve_glpk solves the the MIP model using GLPK

ata_append_constraints(x, mat, dir, rhs)

ata_form_index(x, forms, collapse, internal_index)

ata_obj_coef(x, coef, compensate)

ata_solve_lpsolve(x, time_limit, message, ...)

ata_solve_glpk(x, time_limit, message, ...)

`mat`	coefficient matrix
`dir`	direction
`rhs`	right-hand-side value
`forms`	indices of forms
`collapse`	`TRUE` to collaspe forms into one form
`internal_index`	`TRUE` to use internal form indices
`coef`	coefficients
`compensate`	`TRUE` to combine coefficients
`time_limit`	the time limit in seconds passed along to solvers
`message`	`TRUE` to print messages from solvers
`...`	additional control parameters for solvers