1. A computer implemented method, comprising: accessing, by a computer system, input data comprising: training data comprising a first plurality of data records, each of the first plurality of data records having a numeric data value for each of a plurality of variables; and a second plurality of data records, each of the second plurality of data records having a numeric data value for at least one of the plurality of variables; identifying, by the computer system, at least a first not fully specified data record within the second plurality of data records that does not include at least a first numeric data value for at least a first variable of the plurality of variables; determining, automatically by the computer system and based on the training data, a relationship between the first variable and at least one other variable in the plurality of variables, wherein determining the relationship comprises: generating, using a machine learning technique and the first plurality of records in the training data, a mathematical model representing the relationship between the first variable and the at least one other variable; and obtaining, using the mathematical model representing the relationship between the first variable and the at least one other variable, at least the first numeric data value for the first variable in the first not fully specified data record.