not a straight line calculation

[patjallan]

Hi all...

A friend of mine works for an online ad company. He is looking for a formula that will work to track ad expenses for a sample customer. The idea is based an a 12 month/365 day claendar and the beginning day cost of advertising is $0.00. On day 365, the amount is $5,000,000.00. This is not a straight line calculation, but a more parabolic/curve graph. Knowing the "curve" could be at different shapes (but always summetrical) I need to create the formula for this problem. Now, if I remember correctly, a straight line formula is y=x2 (squared). A true parabolic curve using a similar formula, I am told, will continue to go up indefinitely.

The formula he cannot figure out. I am looking to see if anyone can help me with this.

Thanks
Pat

[patjallan]

Hi all...

A friend of mine works for an online ad company. He is looking for a formula that will work to track ad expenses for a sample customer. The idea is based an a 12 month/365 day claendar and the beginning day cost of advertising is $0.00. On day 365, the amount is $5,000,000.00. This is not a straight line calculation, but a more parabolic/curve graph. Knowing the "curve" could be at different shapes (but always summetrical) I need to create the formula for this problem. Now, if I remember correctly, a straight line formula is y=x2 (squared). A true parabolic curve using a similar formula, I am told, will continue to go up indefinitely.

The formula he cannot figure out. I am looking to see if anyone can help me with this.

Thanks
Pat

[MrShorty]

The worst part of something like this is when you get off to a bad start

Now, if I remember correctly, a straight line formula is y=x2 (squared).

The generic formula for a straight line is y=ax+b. A parabola adds one additional term: y=ax^2+bx+c.

Beyond that, I'm afraid I can't readily help with the problem. A couple of questions for you:

1) Is this a curve fitting/regression problem? If so, curve fitting is an oft discussed topic, and there are many good web-sites with tutorials describing how to do regression with polynomials in Excel. I would suggest putting "Excel LINEST regression" into your favorite search engine.

2) What does this mean?

Knowing the "curve" could be at different shapes (but always summetrical)

Parabolas are symmetric about the line x=-b/2a, but the kind of symmetry a parabola exhibits doesn't seem applicable to this problem.

[patjallan]

I have forwarded on your comments to my friend. After I have done additonal research, I find you are correct as far as I understand his question. If he requires additional "help", I will post a reply here.

Your comments were most helpful to me and I thank you.

Pat