Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Topic: sum of exponentials
Replies: 9   Last Post: Nov 24, 2012 7:16 PM

 Messages: [ Previous | Next ]
 dwi Posts: 17 Registered: 10/18/12
Re: sum of exponentials
Posted: Nov 23, 2012 9:54 AM

"Roger Stafford" wrote in message <k8lqar\$4po\$1@newscl01ah.mathworks.com>...
> "dwi" wrote in message <k8l6sb\$2fj\$1@newscl01ah.mathworks.com>...
> > I have a matrix whose data are interrupted by sequences of zeros. I need every time that there's a zero value to substitute it with a sum of exponentials using the previous data, eg:
> > x=[x1 x2 x3 0 0 0 x7 0 0]
> > When i find the first zero in the element x4 I want:
> > x4=(x3*e^(-1)+x2*e^(-2)+x1*e^(-3))/(e^(-1)+e^(-2)+e^(-3));
> > However, when I find the second zero value I need to calculate the same expression but without using the previous recalculated values. That is,
> > x4=x5=x6
> > and for x8 I will use only the values in x7,x3,x2,x1 and then x8=x9 etc
> > And all this for a 180000-length data.
> > Any ideas on how to do this?

> - - - - - - - - -
> a = 0; b = 0;
> for k = 1:length(x)
> if x(k) ~= 0
> a = x(k) + a*e^(-1);
> b = 1 + b*e^(-1);
> else
> x(k) = a/b;
> end
> end
>
> Roger Stafford

Thank you for your answer but if I use this the index of the exponent never changes.I want it to decrease as k increases, and i don't know hot to calculate a sum like this.

Date Subject Author
11/22/12 dwi
11/22/12 Roger Stafford
11/23/12 dwi
11/23/12 dwi
11/23/12 dwi
11/23/12 dwi
11/23/12 Roger Stafford
11/24/12 dwi
11/24/12 Roger Stafford
11/24/12 dwi