Getting Rid of Error Message

[rvExcelNewTip]

I have a "simple" logarithmic function: - log(1-$a1)/log(1+$i$1) where
the $a colomn varies between 0 and 0.9999 and $i$1 is always positive.
A xy chart is drawn for this function with a logarithmic Y-axis.

Displaying the chart always provokes an arror message: (something like)
-Negative or null values cannot be correctly drawn in logarithmic
charts....-.

For as far as my algebaic knowledge goes, this function (within the
data range) never gets negative. Why the error message? And more
inmportantly, how to get rid of it?

Turning DisplayAlerts off is NOT an option, as the Workbook that
contains that function can display valid messages.

 

[Jon Peltier]

Are there any error bars which might lead to a negative number?

- Jon
-------
Jon Peltier, Microsoft Excel MVP
Peltier Technical Services
Tutorials and Custom Solutions
http://PeltierTech.com/
_______


"rvExcelNewTip" <[email protected]>
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[rvExcelNewTip]

The error shows even if the chart is drawn without any error bars. As
soon as you switch the scale of the Y-axis to logarithmic, you get it.

PS: I do have a problem with error bars in a logarithmic plot in a
related problem:
http://www.excelforum.com//showthread.php?t=498625&goto=newpost

 

[Jon Peltier]

Any blank cells in the source data range?

- Jon


"rvExcelNewTip" <[email protected]>
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[rvExcelNewTip]

No blank cells in the source data range!
Excel version 2003

I should perhaps add that the offending error message suggests the
following advise:

- Enter only values that are positive in the cells used by the chart
- Unselect the logarithmic scale

I also changed the formula to -ABS(LOG(1-$A1)/LOG(1+$I$1))-, thereby
eliminating the leading minus sign. Same result.

Apparently, Excel is suspicious of the -ABS(LOG(1-$A1))- part of the
formula. If you substitute this test formula for the original one, the
message persists.

The -1-$A1- part could theoretically result in a negative argument for
the -LOG- function, but the actual data don't as the values in the -$A-
column are between 0 and 0.999

In my opinion the resulting message is misplaced, not to say an error
(or should I say bug in this case?)

Thanks Jon for your continuing support.

 

[Jon Peltier]

-ABS(LOG(1-$A1)/LOG(1+$I$1))-

I'm confused by your apparent use of hyphen/minus sign for quotes. Do you
mean this?

"ABS(LOG(1-$A1)/LOG(1+$I$1))"

Since $A1 is always less than 1, 1-$A1 is always positive, but log(1-$A1) is
either zero (if $A1 is 0) or negative (if $A1>0 and <0.999). If you're
plotting this function on a log scale, Excel will reject it. If you're
plotting ABS(this function) on the log scale, and there's an instance where
$A1=0, then ABS(the function)=0 and Excel will again reject it.

- Jon
-------
Jon Peltier, Microsoft Excel MVP
Peltier Technical Services
Tutorials and Custom Solutions
http://PeltierTech.com/
_______


"rvExcelNewTip" <[email protected]>
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[rvExcelNewTip]

I'm confused by your apparent use of hyphen/minus sign for quotes. D
you
mean this?
"ABS(LOG(1-$A1)/LOG(1+$I$1))"

Jon,

It's my turn to be confused In my view of the forum messag
the hyphens don't show up. I used (and hopefully this comes throug
unscattered) either --LOG(1-$A$1)/LOG(1+$I$1)- o
-ABS(LOG(1-$A$1)/LOG(1+$I$1))-

Since $A1 is always less than 1, 1-$A1 is always positive, bu
log(1-$A1) is
either zero (if $A1 is 0) or negative (if $A1>0 and <0.999). If you're
plotting this function on a log scale, Excel will reject it. If you're
plotting ABS(this function) on the log scale, and there's an instanc
where
$A1=0, then ABS(the function)=0 and Excel will again reject it.

You hit the nail on the head: I should start the $A range at a valu
other than zero (e.g. 0.001) and then the message disappears. Excel
after all, was right! Many Thank

 

[Jon Peltier]

You should be using plain text in these forums, if you're not already. The
two bits you included in your first para were:

--LOG(1-$A$1)/LOG(1+$I$1)- [two leading hyphens and one trailing]
-ABS(LOG(1-$A$1)/LOG(1+$I$1))- [single leading and trailing hyphens]

- Jon
-------
Jon Peltier, Microsoft Excel MVP
Peltier Technical Services
Tutorials and Custom Solutions
http://PeltierTech.com/
_______


"rvExcelNewTip" <[email protected]>
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