Concatenating Unique and Nonmissing Data
I have a data table describing the tool history for a series of semiconductor lots. In some instances, the lots can split and be run across different tools for the same processing step. In such case, I would like to create a column with each tool concatenated to indicate that > 1 tool was involved. With a lot of help, I have gotten to the point where I can identify the lots, steps and substeps ...