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Science Forum Index » Math - Numerical Analysis Forum » Finding the functions F(x) and f(x)
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Message |
| John Nore |
Posted: Sat Mar 10, 2007 1:44 pm |
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Guest
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Hi all, I am trying to find the functions F(x) and f(x), if it is possible.
I have one row of data in the style:
Ak
Ak-1
..
..
..
A3
A2
A1
A0
I also have:
A0= F(1)+ F(2)+ F(3)+... F(k)
A1= F(2)+ F(3)+ F(4)+... F(k)
..
..
..
etc
F(x)= (1/x)* f(Ax)
F(1)> F(2)> F(3)> ...> F(K) <=>
<=> f(A1)> (1/2)*f(A2)> (1/3)*f(A3)>...> (1/k)*f(Ak)
A0= F(1)+ F(2)+ F(3)+ ... + F(k) =>
=> A0= f(A1)+ (1/2)*f(A2)+ (1/3)f(A3)+... + (1/k)*f(Ak)
A1= f(A2)+ (1/2)*f(A3)+... + (1/(k-1))*f(Ak)
A0- A1= f(A1)- (1/2)*f(A2)- (1/6)*f(A3)- (1/12)*f(A4)- ... -( 1/( ( k(k-1) ) )*f(Ak) =>
k
=> f(A1)= A0 - A1 + S( (1/( v*(v-1) ))* f(Av) ) [where S means sum].
n=2
How may I find the "body" of f(x) and F(x), if it is possible? |
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| Peter Spellucci |
Posted: Mon Mar 12, 2007 3:36 am |
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In article <1173548684.181728@athprx03>,
John Nore <jnore@no.spam> writes:
Quote: Hi all, I am trying to find the functions F(x) and f(x), if it is possible.
I have one row of data in the style:
Ak
Ak-1
.
.
.
A3
A2
A1
A0
I also have:
A0= F(1)+ F(2)+ F(3)+... F(k)
A1= F(2)+ F(3)+ F(4)+... F(k)
you write this as if the number of summands on the right would be the
same but they aren't , or his there a typo?
Ak= F(k) ??????
hence F(i)=A(i)-A(i-1) i=1,...,k
Quote:
F(x)= (1/x)* f(Ax)
hence i*F(i)= f(Ai) = i*(A(i)-A(i-1)) i=1,...,k
you have the data A0,..,Ak
and want to know how the function f(.) might look like?
no knowledge of any other kind?
f(.) could indeed be an arbitrary combination of almost
arbitrary functions
then it depends on your later uses of f(.) what to do
maybe you look at the graph and decide on this,
whether to "fit" the data list (i,f(Ai)) by some suitable linear
combination
or you use an interpolating spline or whatever
hth
peter
Quote:
F(1)> F(2)> F(3)> ...> F(K) <=
=> f(A1)> (1/2)*f(A2)> (1/3)*f(A3)>...> (1/k)*f(Ak)
A0= F(1)+ F(2)+ F(3)+ ... + F(k) =
=> A0= f(A1)+ (1/2)*f(A2)+ (1/3)f(A3)+... + (1/k)*f(Ak)
A1= f(A2)+ (1/2)*f(A3)+... + (1/(k-1))*f(Ak)
A0- A1= f(A1)- (1/2)*f(A2)- (1/6)*f(A3)- (1/12)*f(A4)- ... -( 1/( ( k(k-1) ) )*f(Ak) =
k
=> f(A1)= A0 - A1 + S( (1/( v*(v-1) ))* f(Av) ) [where S means sum].
n=2
How may I find the "body" of f(x) and F(x), if it is possible? |
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| Guest |
Posted: Wed Mar 21, 2007 9:06 am |
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On Mar 12, 3:36 pm, spellu...@fb04373.mathematik.tu-darmstadt.de
(Peter Spellucci) wrote:
Quote: In article <1173548684.181728@athprx03>,
John Nore <j...@no.spam> writes:
Hi all, I am trying to find the functionsF(x) andf(x), if it is possible.
I have one row of data in the style:
Ak
Ak-1
.
.
.
A3
A2
A1
A0
I also have:
A0=F(1)+F(2)+F(3)+...F(k)
A1=F(2)+F(3)+F(4)+...F(k)
you write this as if the number of summands on the right would be the
same but they aren't , or his there a typo?
Ak=F(k) ??????
.
.
.
etc
henceF(i)=A(i)-A(i-1) i=1,...,k
F(x)= (1/x)*f(Ax)
hence i*F(i)=f(Ai) = i*(A(i)-A(i-1)) i=1,...,k
you have the data A0,..,Ak
and want to know how the functionf(.) might look like?
no knowledge of any other kind?
f(.) could indeed be an arbitrary combination of almost
arbitrary functions
then it depends on your later uses off(.) what to do
maybe you look at the graph and decide on this,
whether to "fit" the data list (i,f(Ai)) by some suitable linear
combination
or you use an interpolating spline or whatever
hth
peter
F(1)>F(2)>F(3)> ...>F(K) <=
=>f(A1)> (1/2)*f(A2)> (1/3)*f(A3)>...> (1/k)*f(Ak)
A0=F(1)+F(2)+F(3)+ ... +F(k) =
=> A0=f(A1)+ (1/2)*f(A2)+ (1/3)f(A3)+... + (1/k)*f(Ak)
A1=f(A2)+ (1/2)*f(A3)+... + (1/(k-1))*f(Ak)
A0- A1=f(A1)- (1/2)*f(A2)- (1/6)*f(A3)- (1/12)*f(A4)- ... -( 1/( ( k(k-1) ) )*f(Ak) =
k
=>f(A1)= A0 - A1 + S( (1/( v*(v-1) ))*f(Av) ) [where S means sum].
n=2
How may I find the "body" off(x) andF(x), if it is possible? |
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