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- - **Re: Algorithm to solve equation for variable**
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Re: Algorithm to solve equation for variableDan wrote:
> I am looking for an algorithm to solve an equation for any particular > variable. For example, if I have the equation y = w * h + l (actually > I have y = w h * l + because I'm using postfix notation), I need an > algorithm that can solve the equation for any of w, h, l. > > I only support the four basic operators in my equations ( + - * / ) > and do not support functions. The way I store the equation is in a > container; each item in the container is either a variable name or an > Integer representing the operation, where + is 2, - is 3, * is 4 and / > is 5. Can you limit the order of the equation with respect to the variable for which you're solving? If not, I'm afraid you'll have a tough time finding a deterministic solution. If you can (and the order is 1), then this isn't too difficult. You would divide each side of the equation into terms (pieces that are all multiplied together), and get all the terms *with* the variable on one side, and all the terms without it on the other. Then you'd remove the variable and divide the side that didn't have it by the side that did, using polynomial division. If you need to solve quadratic and other more complex equations, then you've got harder work. Is that what you wanted? -- www.designacourse.com The Easiest Way to Train Anyone... Anywhere. Chris Smith - Lead Software Developer/Technical Trainer MindIQ Corporation |

Re: Algorithm to solve equation for variable"Dan" <daniel.grieves@motorola.com> wrote in message
news:97a39f4.0306301009.451b972@posting.google.com ... > I obviously had not thought hard enough about what I wanted! I guess > in my mind I had limited the problem so that each variable appeared > only once in the equation. Sorry for the half-baked question. I'm not sure your question is really half-baked, perhaps you just did not explain it very well. Perhaps if you gave an example of what you mean by solving the equation. Your original problem statement gave one equation with 4 variables. There are typically an infinite number of combination of the four variables for which the equation will hold. Perhaps what you meant was that given all but one of the variables solve for the remaining one. That is doable, but there probably isn't much off the shelf solvers for that except something like Maple. -- Dale King |

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