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General => The Lobby => Topic started by: snorkel on June 07, 2010, 09:50:33 PM

Title: help me make an equation
Post by: snorkel on June 07, 2010, 09:50:33 PM
I forgot how to do this

I have this data:

7 days in business --------- 5 servers
14 days -------- 13
21 days --------- 21
28 days --------- 42
35 days --------- 50
42 days --------- 59
49 days --------- 80
56 days --------- 120


I need to make a function where the variable is the number of days in business and the output is the projected number of servers. I can't find my graphing calculator
Title: Re: help me make an equation
Post by: strongbad on June 07, 2010, 09:55:52 PM
y=ax+b
i'm too lazy to analyze your data though
Title: Re: help me make an equation
Post by: bluaki on June 07, 2010, 10:03:46 PM
Don't feel like making a function, but here's a plot:
[spoiler](http://imgur.com/4H9m1.png)[/spoiler]

The last data point of 56 days and 120 servers looks like an outlier. With that, it looks roughly like exponential growth. Without, it looks roughly linear.
Title: Re: help me make an equation
Post by: snorkel on June 07, 2010, 10:06:29 PM
Quote from: Strongbab on June 07, 2010, 09:55:52 PM
y=ax+b
i'm too lazy to analyze your data though


yeah but I need like a quadratic function that accounts for growth, or something, not a linear average

Title: Re: help me make an equation
Post by: strongbad on June 07, 2010, 10:09:53 PM
(http://imgur.com/t64iu.jpg)
with trendline, r squared value, and equation, although it doesn't really makes sense to me

EDIT: oh nvm that's not what you want lol
idk how to do anythign else
Title: Re: help me make an equation
Post by: spaceman on June 07, 2010, 10:19:19 PM
I started messing with trendlines and then realized that's not what you wanted
Title: Re: help me make an equation
Post by: Socks on June 07, 2010, 11:17:42 PM
i'm not a math man, but it looks like exponential functions are what you're looking for, particularly exponential growth.

Title: Re: help me make an equation
Post by: bluaki on June 08, 2010, 03:31:13 AM
Quote from: Strongbab on June 07, 2010, 10:09:53 PM
with trendline, r squared value, and equation, although it doesn't really makes sense to me

EDIT: oh nvm that's not what you want lol
idk how to do anythign else
y=2.1463x - 18.857 from that image is pretty much the function he needs.
Using any x value for number of days, it'd give a rough estimate for number of servers if the known trend continues.

Exponential growth doesn't seem like it'd be as suitable, because the type of server gain in this context isn't the sort of thing I'd expect to raise that fast.
Title: Re: help me make an equation
Post by: snorkel on June 08, 2010, 05:12:42 AM
Quote from: bluaki on June 08, 2010, 03:31:13 AM
y=2.1463x - 18.857 from that image is pretty much the function he needs.
Using any x value for number of days, it'd give a rough estimate for number of servers if the known trend continues.

Exponential growth doesn't seem like it'd be as suitable, because the type of server gain in this context isn't the sort of thing I'd expect to raise that fast.


or would you
Title: Re: help me make an equation
Post by: BlackDS on June 08, 2010, 12:18:21 PM
Get a TI graphing calcualtor, and press a lot of buttons, and you will get an equation. [Stat] [edit] (put in your data) [Stat] [quadReg] [L1] [,] [L2] [,] [stat] [Y-var] [y1] [enter]

And people say that algebra 2 teaches you nothing (which I have a final for tomorrow wish me luck!)
Title: Re: help me make an equation
Post by: snorkel on June 08, 2010, 07:31:58 PM
Quote from: BlackDS on June 08, 2010, 12:18:21 PM
Get a TI graphing calcualtor, and press a lot of buttons, and you will get an equation. [Stat] [edit] (put in your data) [Stat] [quadReg] [L1] [,] [L2] [,] [stat] [Y-var] [y1] [enter]

And people say that algebra 2 teaches you nothing (which I have a final for tomorrow wish me luck!)


yes I remember how to do it on A CALC but I think I sold mine for coke money awhile ago.
Title: Re: help me make an equation
Post by: strongbad on June 18, 2010, 12:23:16 PM
Quote from: wziard on June 08, 2010, 07:31:58 PM
yes I remember how to do it on A CALC but I think I sold mine for coke money awhile ago.

ಠ_à²