Hi @kwikpils , and welcome to the Knime Community.

I checked your link, but I ended up not getting the file - have to agree to terms and services which I don’t have the patience to read and I don’t know that site.

I think there might be an issue with your data, though Knime should still see the column and only complain about the data after processing it - the Math formula should only look for numeric columns when being configured.

I tried the following without any problem. I used this sample data:

The Math Formula can see the 2 numeric columns, including the Double one:

I also did a test with a GroupBy:

which generated this:

And the Math Formula saw the new column:

Can you upload your file directly in the forum?

EDIT: Ahh! Found the issue! It’s a column naming issue. It cannot handle the “$” in the name.

Here’s my new test table:

The Math Formula cannot see the column with name “`Custo Desconto (R$)`

”:

You can rename the column before doing the Math Formula and restore the name after, that works.

Rename:

The Math Formula now sees the column:

Restore the name back:

Result:

FYI: Just a comment about what you are trying to do. Multiplying by -1 will indeed convert positives to negatives, but it will also convert negatives to positives. If you want to convert all positives to negatives and leave the negatives as negatives, then you should do `abs($your_column) * -1`

The `abs()`

function converts the value to its absolute value (meaning it converts everything to positive), and by converting everything to positive and then multiplying them with -1 will result all of them to be negative.