Algorithms

23-Jul-08 1:39

I want to implement FDIST function in c#. Can any one tell me what is the formula to calculate FDIST. its arguments are :-
FDIST(x,degrees_freedom1,degrees_freedom2)

X is the value at which to evaluate the function.

Degrees_freedom1 is the numerator degrees of freedom.

Degrees_freedom2 is the denominator degrees of freedom.

thanks in advance

cp987623-Jul-08 12:03

cp9876

23-Jul-08 12:03

Where have you searched so far? Did you look in the excel documentation where it tells you that it implements the F-Distribution? Have you googled F-Distribution?

Peter
"Until the invention of the computer, the machine gun was the device that enabled humans to make the most mistakes in the smallest amount of time."

sumit703423-Jul-08 17:58

23-Jul-08 17:58

I have also googled this and i got this link
http://www.koders.com/c/fid8C33CB0E167B2428AD1774E005CB4373CBEEAAC9.aspx[^]

but still it is not showing correct answer as in ms excel.

sumit703429-Jul-08 18:46

29-Jul-08 18:46

hi I have solved FDIST in C#. now I have to find FINV
Which Returns the inverse of the F probability distribution. If p = FDIST(x,...), then FINV(p,...) = x.

Any idea about this. how to find inverse of the F probability distribution
Syntax

FINV(probability,degrees_freedom1,degrees_freedom2)

Probability is a probability associated with the F cumulative distribution.

Degrees_freedom1 is the numerator degrees of freedom.

Degrees_freedom2 is the denominator degrees of freedom.

thanks in advance

Kok Yuen Li8-Oct-13 22:15

Kok Yuen Li

8-Oct-13 22:15

Hi sumit7034,

I have trying to develop FDIST and FINV function in C# just like what you did. However I don't have any idea how to start with it until I found your post in code project after several days of searching in google. Could you share with me or guide me on this based on your experience?

Do you manage to develop the FINV function?
I read your post mentioning that you manage to resolved the FDIST where the value is as close as what we get from Excel FDIST. Could you share on that?

Thanks. Hope to hear from you soon.

Paul Conrad23-Jul-08 12:13

23-Jul-08 12:13

You might want to look at: http://mathworld.wolfram.com/[^] since you ask for math formulas a lot.

What have you coded so far with the FDIST function? Show what you've done so people don't get the impression you are just throwing a question out there and waiting for someone to do it for you.

"The clue train passed his station without stopping." - John Simmons / outlaw programmer

"Real programmers just throw a bunch of 1s and 0s at the computer to see what sticks" - Pete O'Hanlon

sumit703423-Jul-08 18:38

23-Jul-08 18:38

using formula in this link:
http://mathworld.wolfram.com/F-Distribution.html[^]

i have written a program in c#

public static double FDIST(double x, double m, double n)
{
double result = gamma((n + m) / 2.0) * Math.Pow(n, n / 2) * Math.Pow(m, m / 2) * Math.Pow(x, n / 2-1);
result = result / (gamma(n / 2) * gamma(m / 2)* Math.Pow(m+n*x,(n+m)/2));
return result;
}

private static double gamma(double data) {
if (data == 0.0) return 0;

double p0 = 1.000000000190015;
double []p ={76.18009172947146,
-86.50532032941677,
24.01409824083091,
-1.231739572450155,
1.208650973866179e-3,
-5.395239384953e-6
};

double y=data ; double x = data;
double tmp = x + 5.5;
tmp -= (x + 0.5) * Math.Log(tmp);

double summer = p0;
for (int j=0;j<6;++j) {
summer += (p[j] / ++y);
}
return Math.Exp(0 - tmp +Math.Log(2.5066282746310005 * summer / x));
}

But still i m not getting accurate answer as in ms excel.
please help

Paul Conrad23-Jul-08 18:47

23-Jul-08 18:47

sumit7034 wrote:
not getting accurate answer as in ms excel

How high of a precision do you need? For most folks, 7 or 8 decimal digits ought to be more than sufficient.

Tried your code, and based on some test values at http://www.bettersolutions.com/excel/EDH113/QI547610521.htm[^], your code is not outputting those results.

"The clue train passed his station without stopping." - John Simmons / outlaw programmer

"Real programmers just throw a bunch of 1s and 0s at the computer to see what sticks" - Pete O'Hanlon

Paul Conrad26-Jul-08 11:49

26-Jul-08 11:49

For your project, are you allowed to use Office Interop Libraries?

"The clue train passed his station without stopping." - John Simmons / outlaw programmer

"Real programmers just throw a bunch of 1s and 0s at the computer to see what sticks" - Pete O'Hanlon

sumit703428-Jul-08 18:56

28-Jul-08 18:56

I cant use this library as i have to implement all by logic.
i m building a web application

Paul Conrad28-Jul-08 18:58

28-Jul-08 18:58

Ahhh, that's too bad. I was going to say, that if you could use the Office Interop Library ( me thinks with a web app, you might be able to, not sure how that stands on the MS Office EULA though ), it would be a total slam dunk. How is it coming along, btw?

"The clue train passed his station without stopping." - John Simmons / outlaw programmer

"Real programmers just throw a bunch of 1s and 0s at the computer to see what sticks" - Pete O'Hanlon

sumit703429-Jul-08 18:00

How to find the values of x and y in a 90 degree sector

29-Jul-08 18:00

I have solved FDIST in C#. now I have to find FINV
Which Returns the inverse of the F probability distribution. If p = FDIST(x,...), then FINV(p,...) = x.

Any idea about this.

thanks in advance

pallaka22-Jul-08 20:53

Re: How to find the values of x and y in a 90 degree sector

22-Jul-08 20:53

How to find the values of x and y in a 90 degree sector when a value is provided which you have to place in the sector;

example:
if a value given is in the range of 0 to 100
1) 29
2) 50
3) 100

i need to place them in a 90 degree sector by finding appropriate x and y values
if the value is 100 it should reach to the corner

IS THERE ANY equation exists for it.

|
|
|_____

90 DEG

dojohansen22-Jul-08 21:45

dojohansen

22-Jul-08 21:45

I can only speak for myself but I have not understood what you're trying to ask. Please try to explain the question clearly.

Re: How to find the values of x and y in a 90 degree sector

Stephen Hewitt22-Jul-08 21:52

Stephen Hewitt

22-Jul-08 21:52

I don't understand what you're asking. Can you explain more clearly?

Steve

Re: How to find the values of x and y in a 90 degree sector

pallaka22-Jul-08 22:27

Re: How to find the values of x and y in a 90 degree sector

22-Jul-08 22:27

I will have a values from 0 to 100.
I will get the data ramdomly ranging from 0 to 100
Which i need to place them in a 90deg ARC. 1/4th of circle
means i need to draw a point in that 90deg arc wrt the value i received.
To draw that i should know the x and y coordinates.

Ex
if the value is zero it should draw in the Center of the circle( means in the corner of the 90 deg ARC)
if the value is 50 it should draw in the middle of the ARC
if the value is 100 it shold draw of the circumference of the circle/ ARC

CPallini22-Jul-08 22:05

CPallini

22-Jul-08 22:05

There's a lack of requirements: system has two degrees of freedom ({x,y} with constraints, though) and your requirements provide only one value.
For instance, you may choose to put all of the points at fixed angle, say 45°, using the following formula:

x(n)= y(n) = (100.0 - n) / (100 * pow(2,.5));

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Re: How to find the values of x and y in a 90 degree sector

pallaka22-Jul-08 22:28

Re: How to find the values of x and y in a 90 degree sector

22-Jul-08 22:28

Thanks for ur quick responce. here is the clarificatio of the question

I will have a values from 0 to 100.
I will get the data ramdomly ranging from 0 to 100
Which i need to place them in a 90deg ARC. 1/4th of circle
means i need to draw a point in that 90deg arc wrt the value i received.
To draw that i should know the x and y coordinates.

Ex
if the value is zero it should draw in the Center of the circle( means in the corner of the 90 deg ARC)
if the value is 50 it should draw in the middle of the ARC
if the value is 100 it shold draw of the circumference of the circle/ ARC

CPallini22-Jul-08 22:40

CPallini

22-Jul-08 22:40

pallaka wrote:
if the value is zero it should draw in the Center of the circle( means in the corner of the 90 deg ARC)
if the value is 50 it should draw in the middle of the ARC
if the value is 100 it shold draw of the circumference of the circle/ ARC

This is the opposite of the previous post (wherein you stated 100 should be at the circle center). Anyway it is not difficult to place the point onto the ray
(assuming ray=1)

x(n) = (n * cos(angle)) / 100;
y(n) = (n * sin(angle)) / 100;

But what to do with angle (since you left this degree of freedom free...)?
You may pick a random value or do you want to choose a fixed one (you put only the constraint 0° <= angle <= 90°)?

BTW: If you need to populate randomly (and uniformly) a circular sector, well, that's a completely different matter!

Re: How to find the values of x and y in a 90 degree sector

pallaka22-Jul-08 22:44

Re: How to find the values of x and y in a 90 degree sector

22-Jul-08 22:44

thanks a lot it resolved my problem

You're welcome

CPallini22-Jul-08 22:50

CPallini

22-Jul-08 22:50

pallaka22-Jul-08 22:33