Parametrics enables you to study the effects of changes in ingredient costs or minimum-maximum restrictions on nutrients, ingredients, and ratios without having to change anything in the formula. The Parametrics Report can perform a dozens of formulation solutions fairly quickly. Because parametrics performs its own solutions, the Parametric Report, unlike the other two reports (Solution and Batch), does not require that the formula be previously solved. If you select the “Parametrics” report, you go to the “Parametrics setup” screen where, you see a list of every ingredient, nutrient, and ratio in the formula. To be in a formula, a nutrient or ingredient must either be checked off or included in a ratio.
For each item in the list there are three sets of columns, four columns each for the variables you can track in parametrics: minimum, maximum, and cost. (Cost applies only to ingredients.)
The first column in each set is a check box that indicates you want test that variable. For example, if you want to look at the effect of cost changes on corn grain, you check the Cost column on the row for “Corn grain.” The other three columns represent optional factors that you may use to control the output. “From” is the start value.. “To” is the end value. “By” indicates by how much the value is changed for each solution.
The “By” value can be negative, in which case the “From” value needs to greater than the “To” value, or you will get no results. If you leave the “By” value at zero, the computer uses the high value from the solution just completed as the value for next solution. If the By” value is zero, the program will stop if a solution proves infeasible. If you leave the “From” value zero, the program starts at zero. If you leave the “To” value zero, the program stops when it reaches the fixed upper limit of 9999.99.
You can specify more than one variable. For, example you can compare what happens when you let the cost of an ingredient vary and at the same time let the maximum value of a nutrient vary. You can specify more than one variable for the same item. You can, for example, let both the cost and the minimum value of an ingredient vary. Multiple variables can be problematic and cause too many slight variations to be meaningful. Currently Tower Grove Feed limits the number of parametric solutions to 512. You may find that is it better to provide a fixed “By” values when using multiple variables.
You can automatically include items without varying them so that you can see how each solution changes its resulting amount. Check the Auto column at the left side of the page to include an item that does not vary in any of its values. Any minimum or maximum restrictions on an auto-included item will be adhered to in each iteration.