Trend line in Excel

[deacs]

Hi all,

I'm messing around with the trend line function in excel. I see there
are 6 different types of trend/regression types:

- Linear
- Logarithmic
- Polynomial
- Power
- Exponential
- Moving Average


I have a list with 30 data points that I would like to plot on chart
with the different trend/regression lines. I notice that the Power and
Exponential options are greyed out, so that I can not choose them. Is
this because 2 of the 30 numbers are negative?

Thanks!

 

[Bernard Liengme]

That is correct
See also http://www.stfx.ca/people/bliengme/ExcelTips/Polynomial.htm

 

[deacs]

Thanks for the reply. Is there a way around this, so that I can plot the
power and exponential lines? Must I remove the negative numbers?

The data points I have represent monthly costs and I would like to make
projections based off of the raw numbers as reference points with other
bottoms up projections. The months with negative numbers are months
when there were returns within this cost category.

Thanks again for your help.

 

[Jay Somerset]

Thanks for the reply. Is there a way around this, so that I can plot the
power and exponential lines? Must I remove the negative numbers?

The data points I have represent monthly costs and I would like to make
projections based off of the raw numbers as reference points with other
bottoms up projections. The months with negative numbers are months
when there were returns within this cost category.

Thanks again for your help.

One way, although a bit clumsy, would be to add a constant to each number,
so that they are all positive. Plot your trend using whatever function you
choose, and then subtract the same constant from any projection that you
derive from the trend.