Differential Formula

[pattiw]

I need to calculate the difference between 2 numbers (each in their own cell). Sometimes one of the numbers will be a positive number and the other a negative. I currently use Excel to do this calculation, but our customer wants us to incorporate it on their drawings in a table in AutoCAD MEP 2012. Does anyone know how to do this? I have already tried cutting and pasting my formula from Excel into the table in AutoCAD but just get "####" as a result. Thanks.

[Ed Jobe]

Tables are not spreadsheets. They don't calculate values. However, you could insert the spreadsheet as a table and it will be linked to the xls so that if you update the one, the other updates. You could also insert a field using the Forumla type and then specify the cells to add.

[irneb]

Tables are not spreadsheets. ... You could also insert a field using the Forumla type and then specify the cells to add.

Don't these 2 statements slightly contradict each other?

And you don't need to go through the entire insert field process. Select a cell in the table (just single click not editing it) and then Right-click --> Insert --> Formula --> Equation. The cell gets edited with an equal sign stared. The normal arithmetic works fine, e.g. =A1+B1 will add the values in the 1st two cells (same as it does in Excel).

You might have trouble with some other functions in Excel's formula's though. Only stuff like Sum, Average & Count seem to work. I'm guessing your excel formula used ABS, that also seems to work fine.

So say you've got the 2 values in A1 and B1, then to get their difference you could do:

=ABS(A1-B1)

Or if you want the difference between their absolute values:

=ABS(ABS(A1)-ABS(B1))

To format the value, again single-left-click on the cell (or click-drag-select a set of cells), then right-click --> Data Format ...

[Ed Jobe]

Don't these 2 statements slightly contradict each other?

It might seem to be so if you get the same result, but no, as seen by the fact that she got "####" when she copied a formula to the cell. The calculation is a function of the field, not the table.

[Tom Beauford]

It might seem to be so if you get the same result, but no, as seen by the fact that she got "####" when she copied a formula to the cell. The calculation is a function of the field, not the table.

If the table in the drawing was a portion of the one in Excel the cell references may not match explaining the "####" when she copied a formula to the cell. All the suggested methods should work, but copying an Excel formula to the cell without checking cell references and making sure the functions are supported by AutoCAD will often cause "####".

[irneb]

Yep. And also an acad table doesn't "default" values to 0 as Excel does. Even if you use a formula field (or simply a table formula as per my previous post) it would display #### if the cells it's pointing to don't contain valid numbers (even if they're empty).

So it's different to being a spreadsheet yes. But it works much the same where those differences don't apply. Actually I'd compare an acad table to a word-table rather than an Excel Spreadsheet. They have much the same limitations.