"Goal Seek" from Excel in Javascript
Michal
Seek" in Excel?
For example:
var a=8;
var b=6;
function c(a,b) {
return a*b;
}
And now I want that "c" will return me 56 and I want to do that only
by changing "b" and this "goal seek" function will return me solution
that "b" must be equal 7
I hope I didn't explain too chaotic.
I tried to find that on google but without any results.
Thanks in advance
Michael
Gregor Kofler
Perhaps this for a start:
http://en.wikipedia.org/wiki/Newton%27s_method
Gregor
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Dr J R Stockton
8g2000hsy.googlegroups.com>, Fri, 16 May 2008 02:31:12, Michal
<ret...@gmail.com> posted:
>For example:
>var a=8;
>var b=6;
>function c(a,b) {
> return a*b;
>}
>
>And now I want that "c" will return me 56 and I want to do that only
>by changing "b" and this "goal seek" function will return me solution
>that "b" must be equal 7
Go to <URL:http://www.merlyn.demon.co.uk/js-demos.htm#FZ>, insert
in the textarea
function c(a,b) { return a*b; }
c(8, X) - 56
put Min X =, say, 0 and Max X = 50, press Find, and read the answer.
Then read the whole page, and View Source to find out how it is done :
it uses
function FindZero(F) { with (F) {
var j, X, XV, HV, LV, Fn = EX1.value
var Lo = userIn(Min1), Hi = userIn(Max1)
X = Lo ; LV = eval(Fn)
X = Hi ; HV = eval(Fn)
if ((LV*HV)>=0) { Ans1.value="Bad bounds" ; return }
for (j=0; j<40; j++) {
X = (Hi+Lo)/2 ; XV = eval(Fn) ; if (XV==0) break
if ((XV*LV)<0) { Hi = X ; HV = XV } else { Lo = X ; LV = XV }
}
Ans1.value="X = "+SigFigExp((Hi+Lo)/2, 8) } }
It's a good idea to read the newsgroup c.l.j and its FAQ. See below.
--
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Michal
>...
> ...
Thank you Dr J R Stockton.
Thats something what I was looking for.
> It's a good idea to read the newsgroup c.l.j and its FAQ. See below.
It's not that I didn't read. I just couldn't find.. Maybe because my
"question" was bad :)
Thanks again
Michael
ad...@faze-1.com
https://github.com/adam-hanna/goalSeek.js
Scott Sauyet
> Michal wrote:
>> Does any one know how to create a function that works similar
> I know this is an old question but it is the first result in a
> google search and I wanted a better solution than the findZero
> function sugested below. So I made my own script which uses the
> Stephensen's Method:
>
> https://github.com/adam-hanna/goalSeek.js
crowded might be a good word. I think rather than a positional
parameter list a configuration object would provide both more
flexibility and more readability:
goalSeek({
testFunction: function(a, b, c) {return a * b * c;},
goal: 140,
params: [4, 5, 3],
position: 2,
tolerance: 0.01, // optional
maxIterations: 1000 // optional
});
//=> 7
goalSeek({
testFunction: function(i, o) {return i * o.a o.b.b1;},
goal: 140,
params: [4, {a: 5, b: {b1: 3}}],
position: 2,
prop: "b.b1", // optional
tolerance: 0.01, // optional
maxIterations: 1000 // optional
});
//=> 7
The other thing I would suggest is that allow an undefined value
as the starting choice for the target parameter. I know that this
would make the algorithm harder to get off the ground; you'll have
to go seeking for an appropriate initial value that works. But it
could lead to a nicer user experience, using a token such as `__`
(which is not defined) as a placeholder:
var __; // (undefined)
goalSeek({
testFunction: function(a, b, c) {return a * b * c;},
goal: 140,
params: [4, 5, __],
position: 2,
tolerance: 0.01, // optional
maxIterations: 1000 // optional
});
//=> 7
Note the change to `params`. This makes it much clearer what you're
looking for.
Cheers,
-- Scott