get_cc_sparse: Create Sparse Constraints Coefficients Data Frame.
In donboyd5/microweight: Tools for Weighting Microdata Files

Description Usage Arguments Details Value

Construct a data frame that represents a sparse matrix with nonzero constraint coefficients. A constraint coefficient is the amount by which a constraint changes if an element of the vector x changes by one unit. This stores only those coefficients that are nonzero, in triplet form, where i is an index identifying which constraint is represented, j is an index identifying which element of the vector x is represented, and nzcc is the value of the nonzero constraint coefficient.

1	get_cc_sparse(xmat, target_names, iweights)

`xmat`	Numeric matrix of unweighted data values in dense form where each row is a household, each column corresponds to a constraint, and each cell is a data value.
`target_names`	Character vector with names for each constraint. One element per column in `xmat`.
`iweights`	Numeric vector of initial weights in the microdata file, one per row in `xmat`.

The data value in xmat multiplied by the initial weight determines how much a constraint will change with a unit change in x, the ratio of the new weight to the initial weight. For example, suppose household number 7 has income of $10,000 then. Suppose that this household is in row 7 of xmat and that column 3 of xmat corresponds to income. If this household has an initial weight of 20, then the constraint coefficient for this cell - how much changing the x value for this household will change the constraint for total income - is 200,000 (20 x 100,000). The constraints coefficient data frame will have a row where i (the index for the constraint, not the household) is 3, j (the index for the household) is 7, and nzcc is 200000.

A data frame representing a sparse matrix of constraint coefficients, with columns:

i: the constraint number
j: an index into x
cname: constraint name, from target_names
nzcc: the nonzero constraint coefficient - the initial weight multiplied by value
iweight: initial weight for this cell
value: data value