By default CODAP will try to determine the if an attribute is categorical or numeric. If any cell has a non-numeric value then the attribute is assumed to be categorical for graphs. However, you can click on the attribute, “Edit Attribute Properties…” and set it to be numeric. In that case the graph will only include numeric cells.
Regarding formulas that require numerical inputs, most will ignore non-numeric cells when calculating values. For, example, the mean of a set of values with mixed numerical and non-numerical cells will just include the numerical cells. See example below:
https://codap.concord.org/releases/latest/static/dg/en/cert/index.html#shared=https%3A%2F%2Fcfm-shared.concord.org%2FU7VigLZ5YR8RI24SD5Kz%2Ffile.json