how do i use excel's natural log function with negative numbers?

im trying to use negative numbers with excel's natural log function, and have
found it doesnt work the way im trying it anyway, has anyone out there used
negative numbers with Excel's natural log function and any sucess?

Hi. If I understand the question, the log of say -5 would be a complex
number.
1.609+3.14159 i

If A1 holds -5, then perhaps two ways...

=IF(A1<0,COMPLEX(LOG(ABS(A1)),PI()),LOG(A1))

or more simply the engineering function...
=IMLN(A1)

--
HTH. :>)
Dana DeLouis
Windows XP, Office 2003


"Craig" <Craig@discussions.microsoft.com> wrote in message
news:BB14205B-0633-46B3-A083-AF26E6CC0CE2@microsoft.com...
> im trying to use negative numbers with excel's natural log function, and
> have
> found it doesnt work the way im trying it anyway, has anyone out there
> used
> negative numbers with Excel's natural log function and any sucess?

Your problem is imaginary:
=IMLOG2("-1+0i")
will return
4.53236014217602i

--
Gary''s Student


"Craig" wrote:

> im trying to use negative numbers with excel's natural log function, and have
> found it doesnt work the way im trying it anyway, has anyone out there used
> negative numbers with Excel's natural log function and any sucess?

im looking for the natural log (NL) or LOGe or e, however you choose to write
it. the exact formulae/equation i wish to enter is Um=U((1-e(-t/T)).
unfortunatley Excel doesn't like it, even when brocken down. could you help
further?

"Gary''s Student" wrote:

> Your problem is imaginary:
> =IMLOG2("-1+0i")
> will return
> 4.53236014217602i
>
> --
> Gary''s Student
>
>
> "Craig" wrote:
>
> > im trying to use negative numbers with excel's natural log function, and have
> > found it doesnt work the way im trying it anyway, has anyone out there used
> > negative numbers with Excel's natural log function and any sucess?

Dana Hi, this was of some help but a little hard for me to understand, here
is the exact equation i wish to put into excel - Um = U(1-e(-t-T)), in my
cells i would have for example A1 = -t, U is constant & T is constant. could
you help further. i believe the reason the trouble occurs is also because im
not using LOG im using Natural LOG (NL).

"Dana DeLouis" wrote:

> Hi. If I understand the question, the log of say -5 would be a complex
> number.
> 1.609+3.14159 i
>
> If A1 holds -5, then perhaps two ways...
>
> =IF(A1<0,COMPLEX(LOG(ABS(A1)),PI()),LOG(A1))
>
> or more simply the engineering function...
> =IMLN(A1)
>
> --
> HTH. :>)
> Dana DeLouis
> Windows XP, Office 2003
>
>
> "Craig" <Craig@discussions.microsoft.com> wrote in message
> news:BB14205B-0633-46B3-A083-AF26E6CC0CE2@microsoft.com...
> > im trying to use negative numbers with excel's natural log function, and
> > have
> > found it doesnt work the way im trying it anyway, has anyone out there
> > used
> > negative numbers with Excel's natural log function and any sucess?
>
>
>

> = U(1-e(-t-T)),

Hi. I don't really follow. I believe the above equation might be written
like this.
Change 't' and 'T' to your cell references.

=U*(1-EXP(-t-T))

Please post back with any further questions. :>)
--
HTH.
Dana DeLouis
Windows XP, Office 2003


"Craig" <Craig@discussions.microsoft.com> wrote in message
news:15CE0F8F-2950-4867-AA2C-B7DB9587DA5C@microsoft.com...
> Dana Hi, this was of some help but a little hard for me to understand,
> here
> is the exact equation i wish to put into excel - Um = U(1-e(-t-T)), in my
> cells i would have for example A1 = -t, U is constant & T is constant.
> could
> you help further. i believe the reason the trouble occurs is also because
> im
> not using LOG im using Natural LOG (NL).
>
> "Dana DeLouis" wrote:
>
>> Hi. If I understand the question, the log of say -5 would be a complex
>> number.
>> 1.609+3.14159 i
>>
>> If A1 holds -5, then perhaps two ways...
>>
>> =IF(A1<0,COMPLEX(LOG(ABS(A1)),PI()),LOG(A1))
>>
>> or more simply the engineering function...
>> =IMLN(A1)
>>
>> --
>> HTH. :>)
>> Dana DeLouis
>> Windows XP, Office 2003
>>
>>
>> "Craig" <Craig@discussions.microsoft.com> wrote in message
>> news:BB14205B-0633-46B3-A083-AF26E6CC0CE2@microsoft.com...
>> > im trying to use negative numbers with excel's natural log function,
>> > and
>> > have
>> > found it doesnt work the way im trying it anyway, has anyone out there
>> > used
>> > negative numbers with Excel's natural log function and any sucess?
>>
>>
>>

Hi. I took e(-t-T) to mean E^(-t-T)

If you really meant the natural log, then perhaps...

=U*(1-LN(-t-T))

or perhaps w/ cell references: =U*(1-LN(-A1-A2))

Again, I'm not sure I follow, so I'm just throwing this out as an idea.
--
HTH. :>)
Dana DeLouis
Windows XP, Office 2003


"Dana DeLouis" <ddelouis@bellsouth.net> wrote in message
news:eqZwvFvYGHA.3392@TK2MSFTNGP03.phx.gbl...
>> = U(1-e(-t-T)),
>
> Hi. I don't really follow. I believe the above equation might be written
> like this.
> Change 't' and 'T' to your cell references.
>
> =U*(1-EXP(-t-T))
>
> Please post back with any further questions. :>)
> --
> HTH.
> Dana DeLouis
> Windows XP, Office 2003
>
>
> "Craig" <Craig@discussions.microsoft.com> wrote in message
> news:15CE0F8F-2950-4867-AA2C-B7DB9587DA5C@microsoft.com...
>> Dana Hi, this was of some help but a little hard for me to understand,
>> here
>> is the exact equation i wish to put into excel - Um = U(1-e(-t-T)), in my
>> cells i would have for example A1 = -t, U is constant & T is constant.
>> could
>> you help further. i believe the reason the trouble occurs is also because
>> im
>> not using LOG im using Natural LOG (NL).
>>
>> "Dana DeLouis" wrote:
>>
>>> Hi. If I understand the question, the log of say -5 would be a complex
>>> number.
>>> 1.609+3.14159 i
>>>
>>> If A1 holds -5, then perhaps two ways...
>>>
>>> =IF(A1<0,COMPLEX(LOG(ABS(A1)),PI()),LOG(A1))
>>>
>>> or more simply the engineering function...
>>> =IMLN(A1)
>>>
>>> --
>>> HTH. :>)
>>> Dana DeLouis
>>> Windows XP, Office 2003
>>>
>>>
>>> "Craig" <Craig@discussions.microsoft.com> wrote in message
>>> news:BB14205B-0633-46B3-A083-AF26E6CC0CE2@microsoft.com...
>>> > im trying to use negative numbers with excel's natural log function,
>>> > and
>>> > have
>>> > found it doesnt work the way im trying it anyway, has anyone out there
>>> > used
>>> > negative numbers with Excel's natural log function and any sucess?
>>>
>>>
>>>
>
>

The log of a negative number will always be complex:

IMLN() for the natural log
IMLOG2() for log based 2
IMLOG10() for log based 10

if you are trying to raise e to a power, then use EXP()
Say A1 contains t
A2 contains T
A3 contains U
A4 contains the formula =A3*(1-exp(-A1/A2))

Here is an example A1 thru A4:

5
7
11
5.615041745


--
Gary's Student


"Craig" wrote:

> im looking for the natural log (NL) or LOGe or e, however you choose to write
> it. the exact formulae/equation i wish to enter is Um=U((1-e(-t/T)).
> unfortunatley Excel doesn't like it, even when brocken down. could you help
> further?
>
> "Gary''s Student" wrote:
>
> > Your problem is imaginary:
> > =IMLOG2("-1+0i")
> > will return
> > 4.53236014217602i
> >
> > --
> > Gary''s Student
> >
> >
> > "Craig" wrote:
> >
> > > im trying to use negative numbers with excel's natural log function, and have
> > > found it doesnt work the way im trying it anyway, has anyone out there used
> > > negative numbers with Excel's natural log function and any sucess?