Extracting data from trendline

Question

Is there anyway to pull a set number of points off of a trendline and have them show up in table form?

Assuming I have a linear trend line set through 10 points of data, I would like to create a table that shows 100 points of data on that same trendline.

Using a graph to do it just seems like the simplest way to explain it, but there may be other ways to expand the amount of data points and get values for the unknown numbers using the trend.

Answer 1

Jeffc09,

You could have Excel display the equation for the trendline, then in an x-y table create a series of x values and use the equation in a formula to calculate the corresponding y values.

Would that help with what you're looking for?

___________________

Regards, Tom

Answer 2

Not really. If my trendline changes the table will not change automatically. If I use a 3rd degree polynomial I will have to change the values of A, B, C, D manually.

The values appearing on the trendline must be somewhere in a register, so I do not really understand why can't we access it.

Rgds

Answer 3

Good answer Tom. It works.

However, if you use a high-degree polynomial (with high powers of x, like x^5), be careful. The equation Excel provides can have some coefficients with only 1 or 2 significant digit, so the data will be very far off for values of x greater than, say 30.

In other words, you will have to tweak the coefficients (to add more significant digits) or the values you generate from the equation will become very inaccurate.

I recommend plotting Excel's trendline along with the your equation-generated data points so that you can fine-tune the coefficients. This is very necessary most of the time.

Answer 4

(1) If you display the equation, be sure to use enough significant digits to avoid errors when you use the coefficients in worksheet formulas.

(2) An alternative is to use worksheet functions, as described by John Walkenbach at http://spreadsheetpage.com/index.php/tip/chart_trendline_formulas/

-  Mike Middleton

TreePlan Software, http://www.TreePlan.com

Decision Tree, Sensitivity, and Simulation Add-Ins for Excel

Answer 5

Yea, thats what I was looking for.  I actually feel kinda dumb for not thinking of it already haha