Negative exponent with cell reference

[DashboardNovice]

I am trying to take a number and raise that to a negative power, but I don't want to hard code that negative power, I want to use a cell reference.

In the attached file, I am entering the S(t) function in cell Q8. To generate the number "e" I am using EXP(1), which works fine. My exponent is raised to "negative t," where the value of t is in cell P8 and down. Here is my current formula:

=1/(1+POWER(EXP(1),-P8))

I am referencing cell P8 but I'm putting a negative in front of it. Somehow I don't think this looks right. Is this correct, or do I need to use " " followed by an ampersand?

I am also trying to plot an S curve, but I can't find examples of a dataset to plot a standard S curve. I would think that starting with 1 would suffice, but it doesn't seem to plot much of an S curve (if my formula is correct). I included a graphic of what I am trying to plot. I don't care about the data, I just want to plot the graph.

 

[NARAYANK991]

Hi ,

Can you post the mathematical formula which you want to implement in Excel , without referring to an Excel formula ?

Narayan

 

[DashboardNovice]

Hi ,

Can you post the mathematical formula which you want to implement in Excel , without referring to an Excel formula ?

Narayan

I did. See the graphic I pasted at cell S20.

 

[NARAYANK991]

Hi ,

The Excel help on the EXP function says this :

Returns e raised to the power of number.

To calculate powers of other bases, use the exponentiation operator (^).
The "^" operator can be used instead of POWER to indicate to what power the base number is to be raised, such as in 5^2.

What I understand this to mean is :

1. The exponentiation operator ^ is the same as the POWER function ; thus 5^2 is the same as =POWER(5 , 2)

2. The EXP function is the shortcut where the base number is the exponential function e. Thus =EXP(3) is a shortcut for =POWER(EXP(1) , 3)

Hence for the mathematical formula which you have posted , which is :


the equivalent Excel formula would be :

=1/(1 + EXP(-1 * t))

For t substitute the values you have in P8 , P9 , P10 ,...

Narayan

 

[DashboardNovice]

Hi ,

The Excel help on the EXP function says this :

What I understand this to mean is :

1. The exponentiation operator ^ is the same as the POWER function ; thus 5^2 is the same as =POWER(5 , 2)

2. The EXP function is the shortcut where the base number is the exponential function e. Thus =EXP(3) is a shortcut for =POWER(EXP(1) , 3)

Hence for the mathematical formula which you have posted , which is :
View attachment 18284

the equivalent Excel formula would be :

=1/(1 + EXP(-1 * t))

For t substitute the values you have in P8 , P9 , P10 ,...

Narayan

Based on your post, it looks like I did do this correctly in my newly attached file here. But the graph didn't come out as expected.

 

[NARAYANK991]

Hi ,

The S-curve will result only when you include negative values of t.

See the attached file.

Narayan

 

[DashboardNovice]

Hi ,

The S-curve will result only when you include negative values of t.

See the attached file.

Narayan

My friend, you are awesome. Thank you again.