Excel Rounding Issue

[seadoggie01]

I'm trying to get a number with (at most) a two digit decimal from an Excel document. The document contains decimals with various lengths. It would seem that using Round() would solve all of my issues, however, it will occasionally round down instead of up. 

This only happens in unusual circumstances that I have yet to be able to make reproduce-able, unfortunately. From what I've gathered from the author of the document, the value is calculated from a formula that is then copied to the final workbook.

When I open up the Excel document (rename as .zip, extract, and inspect \xl\worksheets\[sheet].xml), I found that instead of storing the value as 704,929.695 it stores the value as 704,929.69499999983 internally. I would be okay with this, except that AutoIt prints the value (to the console) as 704,929.695. Excel will round the value in formulas up to 704,929.70 because the value is probably supposed to be 704,929.695?

I found a sort of fix with this:

Func FixRound($vNum, $iDec = Default)
    Return Round(StringStripWS($vNum & " ", 8), $iDec)
EndFunc

Is this an issue related to floating point numbers? Is there a way to see the actual value inside Excel inside AutoIt? Instead of getting the .Value of a cell, I could try using .Text, but this will cause more issues than it will fix, I think

[jchd]

Excel uses its own rules!

Local $v = 704929.69499999983
ConsoleWrite(StringFormat("%.11f", $v) & @LF)
ConsoleWrite($v & @LF)
ConsoleWrite(StringFormat("%.2f", $v) & @LF)
$v = 704929.695
ConsoleWrite(StringFormat("%.11f", $v) & @LF)
ConsoleWrite($v & @LF)
ConsoleWrite(StringFormat("%.2f", $v) & @LF)

 

[seadoggie01]

I don't think I understand. That doesn't round for me... it just truncates

[jchd]

Local $v = 704929.69499999983
ConsoleWrite(StringFormat("%.11f", $v) & @LF)   ; 704929.69499999983
ConsoleWrite($v & @LF)                          ; 704929.695
ConsoleWrite(StringFormat("%.2f", $v) & @LF)    ; 704929.69
$v = 704929.695
ConsoleWrite(StringFormat("%.11f", $v) & @LF)   ; 704929.69499999995
ConsoleWrite($v & @LF)                          ; 704929.695
ConsoleWrite(StringFormat("%.2f", $v) & @LF)    ; 704929.69

ConsoleWrite(Round($v, 2) & @LF)                ; 704929.7
ConsoleWrite(StringFormat("%.2f", Round($v, 2)) & @LF)  ; 704929.70

Like most real numbers, 704929.695 can't be represented exactly in a double. AutoIt rounds the value correctly when asked to.

[seadoggie01]

But that is the weird thing. When Excel stores the value internally as 704929.69499999983 but displays .695 and I read the value from Excel, AutoIt prints the value as .695 but rounds it down like it is .6949

Try this code with the Excel document attached...

#include <Excel.au3>

Main()

Func Main()

    Local $oBook = _Excel_BookAttach("Example.xlsx", "filename")
    If @error Then Exit ConsoleWrite("Can't attach to workbook -- Open it" & @LF)

    Local $vVal = _Excel_RangeRead($oBook, 1, "B1")
    If @error Then Exit ConsoleWrite("Can't read Excel range" & @LF)

    ConsoleWrite($vVal & @LF)                   ; 704929.695
    ConsoleWrite(Round($vVal, 2) & @LF)         ; 704929.69  <- Should Round up?
    ConsoleWrite(Round($vVal & " ", 2) & @LF)   ; 704929.7

EndFunc

 

Example.xlsx

[Nine]

Yes there is some kind of a glitch inside excel, if you rewrite B1 manually then it is working for me (even just doing a del key at the end of the field followed by  a Enter key).

or

If you do $vVal = round($vVal,3) after reading, it is also working.

The problem seems to come on how you created B1, by copying, or by an equation, or other means ?  But the problem lies there, as it seems there is more decimal that it is actually showing...

Edited September 3, 2020 by Nine

[seadoggie01]

Yes, I think the value was creating with a formula that was then copy/paste (values) into another workbook. I think at this point, my best option might be to use Excel to round the values as it properly rounds the value up to .70 even if the value is stored strangely. Something like setting the offset cell to =Round(B1,2) and reading that instead.

[robertocm]

not directly related, but i remember some issues rounding with VBA functions:

Round() and Application.Round use different rounding algorithms, as explained here:

http://www.vbaexpress.com/forum/showthread.php?6889-Solved-Is-It-quot-Round-quot-or-quot-Application-Round-quot

https://stackoverflow.com/questions/265926/round-function-in-excel-worksheet-function-vs-vba

[seadoggie01]

Thanks @robertocm! I never knew that VBA uses Banker's rounding... which is apparently applicable in accounting, though I've never heard anyone mention that here 😐 I was thinking about using Application.Round to fix the issue too, but I guess that won't work either 🤦‍♂️

[Subz]

Have you tried reading the cell as a formula rather than a value?

[jchd]

Things would be much simpler if everything used the least damaging rounding method know as half to even see https://en.wikipedia.org/wiki/Rounding#Round_half_to_even yet the whole article is worth reading carefully.

[seadoggie01]

The problem that I face with rounding is that I'm processing journal entries where a whole penny is the smallest unit, but they're submitted to me with various lengths. Usually, rounding to the nearest whole penny works, but occasionally they don't balance to 0. I'd love to say I have a fix for this, but I honestly just throw it back to the user to fix and restart.

@Subz Reading the formula instead of the value worked perfectly, thank you! I'll need to copy/paste values beforehand, but that's a good idea anyways