# Is There A Free Web Tool For Solving F(x,y) Equations?

• May 5th 2011, 06:12 PM
morphman
Is There A Free Web Tool For Solving F(x,y) Equations?
So I'm embarassed to say I have a degree in computer science and engineering and I'm tweaking with some formulas I'd like to use in a game I'm building, and my math is very rusty--much worse than I thought. I'm trying to find a free tool or website that would present the results of an f(x,y) function in tabular format so I could just eyeball the results of the equation as I make adjustments to the values for x and y... if that makes sense?

For example, I'd like to see all of the results for the following equation:

f(x,y) = (x - y) / (x + y)
where:
x and y are integers
x >= y
y > 0
x < 100 (or some other value that i could plug in myself)

I've found some tools that can kind of show it in 3D format but I can't seem to find one shows results like this:

x y z
2 1 .3333
2 2 0
3 1 .5
3 2 .2
3 3 0
4 1 .6

etc.

Any help would be greatly appreciated! I'm banging my head against the wall...

Thanks,

Embarrassed and Forgetful Math Noobie
• May 6th 2011, 02:27 AM
Ackbeet
Quite honestly, I would write a little computer program to solve this. One for loop inside another for loop should do the trick. Something like this (obviously pseudocode):

Code:

```function f(x,y) = (x-y)/(x+y); print 'x  y  f(x,y)' for x = 1 to 100   for y = 1 to x       print x  y  f(x,y)   end for end for```
• May 6th 2011, 03:24 AM
morphman
Last Resort
Thanks Adrian. I may very well end up doing that but I'm most likely going to be doing this for many equations until I find one that I like. As such, it would be handy to just be able to plug them in to a web page that will do the work for me so I don't have to write bagillions (technical term for many) of this mini programs. If there isn't such a thing then I'll just have to get over it! Thanks for your suggestion nonetheless.
• May 6th 2011, 04:48 AM
Ackbeet
You wouldn't necessarily have to write bagillions of mini programs. Just rewrite your function definition each time.

Here's an alternative: Excel. You could use the row reference function (that is, each cell knows what cell it is) and column reference functions to get your x and y. The fact that y <= x means you would only look at the upper diagonal or the lower diagonal.
• May 6th 2011, 05:03 AM
CaptainBlack
Quote:

Originally Posted by morphman
So I'm embarassed to say I have a degree in computer science and engineering and I'm tweaking with some formulas I'd like to use in a game I'm building, and my math is very rusty--much worse than I thought. I'm trying to find a free tool or website that would present the results of an f(x,y) function in tabular format so I could just eyeball the results of the equation as I make adjustments to the values for x and y... if that makes sense?

For example, I'd like to see all of the results for the following equation:

f(x,y) = (x - y) / (x + y)
where:
x and y are integers
x >= y
y > 0
x < 100 (or some other value that i could plug in myself)

I've found some tools that can kind of show it in 3D format but I can't seem to find one shows results like this:

x y z
2 1 .3333
2 2 0
3 1 .5
3 2 .2
3 3 0
4 1 .6

etc.

Any help would be greatly appreciated! I'm banging my head against the wall...

Thanks,

Embarrassed and Forgetful Math Noobie

Excel (or Gnumeric, or LibreOffice - the new name for OpenOffice), put the x's down the first column and the y's across the first row. Enter f(x,y) in any cell making the row for the y absolute and the column for the x absolute. Copy the formula to all the cells.

However if you really mean what it says in the subject line, that you want to solve an equation of the form f(x,y)=C subject to constraints on x and y you should look at the solver in Excel (I would not recommend the solvers in the other two, as they are not quite as general and complete as that in Excel).

CB
• May 6th 2011, 11:43 AM
morphman
I just did some playing around with Excel 2007 and it is suprisingly easy to do this! I did exactly what you suggested and it works like a charm. I still need to do some tweaking to get the formula to apply correctly on all of the cells but I'm certain this is the right track to my solution. Unfortunately I don't have Excel at home so I'll have to download something else. Thanks for the suggestion.
• May 6th 2011, 11:53 AM
Ackbeet
To whom are you responding?
• May 6th 2011, 04:01 PM
morphman
Excel will work just fine
Quote:

Originally Posted by CaptainBlack
Excel (or Gnumeric, or LibreOffice - the new name for OpenOffice), put the x's down the first column and the y's across the first row. Enter f(x,y) in any cell making the row for the y absolute and the column for the x absolute. Copy the formula to all the cells.

However if you really mean what it says in the subject line, that you want to solve an equation of the form f(x,y)=C subject to constraints on x and y you should look at the solver in Excel (I would not recommend the solvers in the other two, as they are not quite as general and complete as that in Excel).

CB

I just did some playing around with Excel 2007 and it is suprisingly easy to do this! I did exactly what you suggested and it works like a charm. I still need to do some tweaking to get the formula to apply correctly on all of the cells but I'm certain this is the right track to my solution. Unfortunately I don't have Excel at home so I'll have to download something else. Thanks for the suggestion.
• May 6th 2011, 04:03 PM
morphman
Quote:

Originally Posted by Ackbeet
To whom are you responding?

Sorry, i don't use forums very often. I was replying to the previous post that suggested using Excel. I just re-posted via "Reply with quote" so that should clear it up. Phew, I'm on a roll--I got an infraction for my first post being in the wrong forum and then this. Oops!