Joe Thank you for your reply. I found the reason for this error message. I have input data by "import folder". The folder of my data includes a test file that is not needed for the calculation. When I imported the folder and unload this file, a value ("NAN") still existed in the test file's time series. Then the error message popped up when processing the Trace Elements DRS. When I deleted the file and retried to calculate, this message disappeared.