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Old April 18th 06, 12:38 PM posted to microsoft.public.excel.worksheet.functions
Craig
 
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Default 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?

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Old April 18th 06, 01:22 PM posted to microsoft.public.excel.worksheet.functions
Dana DeLouis
 
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Default how do i use excel's natural log function with negative numbers?

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" wrote in message
...
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?



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Old April 18th 06, 01:23 PM posted to microsoft.public.excel.worksheet.functions
Gary''s Student
 
Posts: n/a
Default how do i use excel's natural log function with negative numbers?

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?

  #4   Report Post  
Old April 18th 06, 02:15 PM posted to microsoft.public.excel.worksheet.functions
Craig
 
Posts: n/a
Default how do i use excel's natural log function with negative number

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?

  #5   Report Post  
Old April 18th 06, 02:20 PM posted to microsoft.public.excel.worksheet.functions
Craig
 
Posts: n/a
Default how do i use excel's natural log function with negative number

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" wrote in message
...
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?






  #6   Report Post  
Old April 18th 06, 03:07 PM posted to microsoft.public.excel.worksheet.functions
Dana DeLouis
 
Posts: n/a
Default how do i use excel's natural log function with negative number

= 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" wrote in message
...
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" wrote in message
...
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?






  #7   Report Post  
Old April 18th 06, 03:28 PM posted to microsoft.public.excel.worksheet.functions
Dana DeLouis
 
Posts: n/a
Default how do i use excel's natural log function with negative number

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" wrote in message
...
= 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" wrote in message
...
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" wrote in message
...
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?







  #8   Report Post  
Old April 18th 06, 08:39 PM posted to microsoft.public.excel.worksheet.functions
Gary''s Student
 
Posts: n/a
Default how do i use excel's natural log function with negative number

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?



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