Project exponential growth againt linear timeline

[rgoubet]

Hi,

I have a series of values growing exponentially over time. I'd like to
project the values in the next 5 years, but I can't figure out how to
use the related functions. For instance:

A B
1 2001 2
2 2002 4
3 2003 8
4 2004 16
5 2005 32
6 2006
7 2007
8 2008
9 2009
10 2010

Now, I want to find the function that will yield the series {64, 128,
258, 512, 1024} in cells B6:B10.

For cell B6 (2006):
- TREND(B1:B5;A1:A5;A6) will not result in 64, which is to be expected
since it's not a linear growth;
- GROWTH(B1:B5;A1:A5;A6) does not work at all and returns an error
(#NUM!). It seems that the series in column A should also be
exponential for GROWTH to work. But time is not exponential (luckily).

So which function should I use to project an exponential progression on
the Y axis, along a linear progression (time) in the X axis? If I use
the "Add trendline" in the graph, it does work, by I can't find a way
to get the actual figures.

Thanks in advance for the help.

Kind regards,

Raph

 

[Guest]

Right-click on trendline==>Format Trendline==>Options==>Display equation on
chart

In your specific example, =POWER(2,(year-2000)) gives results you require

HTH

 

[mrgou]

Toppers a écrit :

Right-click on trendline==>Format Trendline==>Options==>Display equation on
chart

In your specific example, =POWER(2,(year-2000)) gives results you require

Thanks. In my real-life instance, the displayed equation is "y =
6105.6e0.6015x", so I'm not really sure what I'm supposed to do with
it. I thought the value (y) for any given year (x) would be:

=6105.6*EXP(0.6015*(year-2000))

But it doesn't match the graph.

Raph

 

[Guest]

For your original data my equation was y=e0.6931x (=EXP(0.6931*(A1-2000))
which gave the following results for 2001- 2010:

1.999905641
3.999622573
7.998867747
15.99698073
31.992452
63.98188523
127.9577332
255.9033924
511.7826381
1023.516985

Do you want post your real-life table and I'll give it a try?