I am hoping that I will be able to check if my data meets certain conditions. For example, if I want only positive values and a column in my data has 2,5, and -3, I want Knime to give me an error message when it sees the -3. Is this possible to do? If so, how? Thank you so much in advance.
I am not aware of a way to send an error message; however you could create a new file with all of the rows that have a negative value on a certain column. You can use the Row Filter node and check the “use range checking” and set the upper bound to 0 (zero). After that then write the records to a file or excel spreadsheet.
You could do the opposite to get all the the rows that only have positive values.
Take a look at the Table Validator node, it has many options to define the desired table structure, including the range of values, it fill fail to execute if the table structure does not match your defined bounds.
Could you try to use the COL_MIN() function? This should give you an indication which column contains negative values?
kn_example_negative_columns.knwf (34.6 KB)