Math.Log

[Joe]

Hello,

I'm using Math.Log10 to get my numbers on the same scale but I'm running
into a problem with negative values.
Math.Log10(-143.73833558) is returning a NaN.

Is there something else I can use?

Sorry if this might seem obvious but I'm not a math wiz.

Thanks,
Joe

[Alberto Poblacion]

"Joe" <jb*******@noemail.noemailwrote in message
news:e8**************@TK2MSFTNGP03.phx.gbl...

I'm using Math.Log10 to get my numbers on the same scale but I'm running
into a problem with negative values.
Math.Log10(-143.73833558) is returning a NaN.

Is there something else I can use?

Sorry if this might seem obvious but I'm not a math wiz.

No, the logarithm of a negative number is not defined in the Real
domain. If you can define more precisely what you mean by "get my numbers on
the same scale" we may be able to suggest an alternative approach.

[Jon Skeet [C# MVP]]

On Sep 30, 3:20*pm, "Joe" <[e-mail]:

I'm using Math.Log10 to get my numbers on the same scale but I'm running
into a problem with negative values.
Math.Log10(-143.73833558) is returning a NaN.

Yes, I'd expect it to.

Is there something else I can use?

Sorry if this might seem obvious but I'm not a math wiz.

Log isn't defined for negative numbers. See
http://msdn.microsoft.com/en-us/libr...10(VS.85).aspx

If you only care about the magnitude, use Math.Log10(Math.Abs(x))

Jon

[Joe]

What I need is to take a range say 10 to 38456 and divide it up into 5
parts.

"Alberto Poblacion" <ea******************************@poblacion.orgwro te
in message news:%2****************@TK2MSFTNGP06.phx.gbl...

"Joe" <jb*******@noemail.noemailwrote in message
news:e8**************@TK2MSFTNGP03.phx.gbl...

>I'm using Math.Log10 to get my numbers on the same scale but I'm running
into a problem with negative values.
Math.Log10(-143.73833558) is returning a NaN.

Is there something else I can use?

Sorry if this might seem obvious but I'm not a math wiz.

No, the logarithm of a negative number is not defined in the Real
domain. If you can define more precisely what you mean by "get my numbers
on the same scale" we may be able to suggest an alternative approach.

[Alberto Poblacion]

"Joe" <jb*******@noemail.noemailwrote in message
news:%2****************@TK2MSFTNGP04.phx.gbl...

What I need is to take a range say 10 to 38456 and divide it up into 5
parts.

... and you want the parts to fit a logarithmic scale, i imagine. You
then want to do the same thing for negative numbers, in such a way that the
scale will be "symetrical" to the positive part. In this case, I suggest
simply taking absolute values and then changing the sign of the result. That
is, if for a positive x you are doing:
double part = Math.Log10(x);
then when x is negative just do:
part = -Math.Log10(-x);
which will give you a "part" between -1 and -5 for x between -10
and -100000.

[\Ji Zhou [MSFT]\]

Hello Joe,

I totally agree with Alberto's suggestion. Since the Math.Log method does
not support the negative parameter. We can pass its absolute value as
parameter into the Math.Log method. Please let us to know if the suggestion
works for your scenario or not. If you have any future questions or
concerns, please do not hesitate to let me know. I will try my best to
provide future help.

Have a nice day!

Best regards,
Ji Zhou (v-****@online.microsoft.com, remove 'online.')
Microsoft Online Community Support

Delighting our customers is our #1 priority. We welcome your comments and
suggestions about how we can improve the support we provide to you. Please
feel free to let my manager know what you think of the level of service
provided. You can send feedback directly to my manager at:
ms****@microsoft.com.

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[=?Utf-8?B?RmFtaWx5IFRyZWUgTWlrZQ==?=]

But that really goes haywire if your data contains values between 0.0 and
1.0. The log10 of those will be negative.

"Alberto Poblacion" wrote:

"Joe" <jb*******@noemail.noemailwrote in message
news:%2****************@TK2MSFTNGP04.phx.gbl...

What I need is to take a range say 10 to 38456 and divide it up into 5
parts.

... and you want the parts to fit a logarithmic scale, i imagine. You
then want to do the same thing for negative numbers, in such a way that the
scale will be "symetrical" to the positive part. In this case, I suggest
simply taking absolute values and then changing the sign of the result. That
is, if for a positive x you are doing:
double part = Math.Log10(x);
then when x is negative just do:
part = -Math.Log10(-x);
which will give you a "part" between -1 and -5 for x between -10
and -100000.

[Alberto Poblacion]

"Family Tree Mike" <Fa************@discussions.microsoft.comwrote in
message news:EB**********************************@microsof t.com...

But that really goes haywire if your data contains values between 0.0 and
1.0. The log10 of those will be negative.

Certainly. In fact, it will approach "minus infinite" as the values
approach zero. I imagine that this is why the Original Poster specified a
range similar to "10 to 38456", otherwise the idea of directly applying a
logarithmic scale needs to be reconsidered.

[Joe]

We have a very wide range of possible numbers coming in. They can
be -15000.90922 to 34000000 and anywhere in between.

We do also have a lot of values very close to 0.

"Alberto Poblacion" <ea******************************@poblacion.orgwro te
in message news:um****************@TK2MSFTNGP02.phx.gbl...

"Family Tree Mike" <Fa************@discussions.microsoft.comwrote in
message news:EB**********************************@microsof t.com...

>But that really goes haywire if your data contains values between 0.0 and
1.0. The log10 of those will be negative.

Certainly. In fact, it will approach "minus infinite" as the values
approach zero. I imagine that this is why the Original Poster specified a
range similar to "10 to 38456", otherwise the idea of directly applying a
logarithmic scale needs to be reconsidered.

[Alberto Poblacion]

"Joe" <jb*******@noemail.noemailwrote in message
news:ec**************@TK2MSFTNGP04.phx.gbl...

We have a very wide range of possible numbers coming in. They can
be -15000.90922 to 34000000 and anywhere in between.

We do also have a lot of values very close to 0.

If the objetive is to break the range of numbers into several parts, you
will have to give some thought as to how you want those parts to be made.
For instance, if you have a number such as 0.001 coming in, its logarithm
will be -3. So it's probably not adequate to be used as a "number of part".
Depending on how you want to group your data you may wish to use a
"mixed" approach where you first apply a fixed criterion to separate the
numbers and then apply a logarithmic scale to some groups. For instance,
first of all divide your numbers into three groups: less than -10,
between -10 and 10, and more than 10. Then apply Logs (as discussed earlier)
to the first and last group to divide them in "parts", while leaving those
in the middle to belong to yet another "part". This may or may not be
adequate for you; it all depends on how you want your numbers classified.

[\Ji Zhou [MSFT]\]

Hi Joe,

If your number x can be in the range from -15000.90922 to 34000000, an easy
and simple way is to add 15002 to the x. So all numbers will be in the
range from 1.09078 to 34015002. So, we can use it as the parameter of the
Math.Log10() directly. But I am not sure if this is the best approach to
your demand. As Alberto has indicated, this issue depends on how you want
to classify your numbers. Could you please share what is in your mind, so
we can give future help on this.
Best regards,
Ji Zhou
Microsoft Online Community Support

=================================================
Delighting our customers is our #1 priority. We welcome your comments and
suggestions about how we can improve the support we provide to you. Please
feel free to let my manager know what you think of the level of service
provided. You can send feedback directly to my manager at:
ms****@microsoft.com.

This posting is provided "AS IS" with no warranties, and confers no rights.
=================================================

[\Ji Zhou [MSFT]\]

Hello Joe,

I am writing to check the status of the issue on your side. Could you
please let me know if the suggestion works for you or not? If you have any
questions or concerns, please feel free to let me know. I will be more than
happy to be of assistance.

Have a great day!

Best regards,
Ji Zhou (v-****@online.microsoft.com, remove 'online.')
Microsoft Online Community Support

=================================================
Delighting our customers is our #1 priority. We welcome your comments and
suggestions about how we can improve the support we provide to you. Please
feel free to let my manager know what you think of the level of service
provided. You can send feedback directly to my manager at:
ms****@microsoft.com.

This posting is provided "AS IS" with no warranties, and confers no rights.
=================================================