[Scilab-users] Summation query in Scilab

[Serge Steer]

Le 13/12/2012 07:56, Lester Anderson a écrit :
> Hi Serge
>
> A quick question. In the context of the equation, what is the purpose 
> of the ones(t) part? The help states that this creates a matrix 
> composed of ones.

(B./(m1.^3*%pi).*sin(m1*%pi/B)) is a column vector, the multiplication by ones(t) which is a row vector  is a way to create a matrix with identical columns
. Ina similar mannerm1.^2*t
  creates a matrix multiplying the column vectorm1.^2  by the row vector t

> g=c*sum((B./(m1.^3*%pi).*sin(m1*%pi/B))*ones(t).*exp(-(m1.^2*t/tau)),1);
> Probabaly a very simple answer.
>
> Cheers
>
> Lester
>
> On 12 December 2012 22:46, Lester Anderson <arctica1963 at gmail.com 
> <mailto:arctica1963 at gmail.com>> wrote:
>
>     Many thanks Serge :) That worked great!
>     Helps to see how the syntax should work.
>
>     Cheers
>
>     Lester
>
>
>     On 12 December 2012 22:29, Serge Steer <serge.steer at inria.fr
>     <mailto:serge.steer at inria.fr>> wrote:
>
>         I think the following code fullfil your wish...
>
>
>         n  =  0:1:20  ;// series in the expansion
>         B  =  1.5;  //beta factor
>         Tm  =  1300*274.15;  //base-lithosphere temperature [C]
>         tau  =  62.8;  //lithosphere cooling thermal decay constant [Ma]
>         a  =  125000;  //equilibrium lithospheric thickness [m]
>         alpha  =  3.28e-5  ;//thermal expansion coefficient K^-1
>         // Tm needs to be converted to Kelvin - multiply by 274.15
>         rho  =  3300;
>         t  =  0:5:150;  //lithosphere age [Ma]
>         G  =  6.67e-11;
>
>         // LTGA with increasing age of oceanic lithosphere
>
>         c=8*G*alpha*rho*a*Tm/%pi;
>         m=(0:20)';m1=2*m+1;
>         g=c*sum((B./(m1.^3*%pi).*sin(m1*%pi/B))*ones(t).*exp(-(m1.^2*t/tau)),1);
>         clf;plot(t,g)
>
>
>         Serge Steer
>         ------------------------------------------------------------------------
>
>             *De: *"Lester Anderson" <arctica1963 at gmail.com
>             <mailto:arctica1963 at gmail.com>>
>             *À: *"International users mailing list for Scilab."
>             <users at lists.scilab.org <mailto:users at lists.scilab.org>>
>             *Envoyé: *Mardi 11 Décembre 2012 08:16:01
>             *Objet: *[Scilab-users] Summation query in Scilab
>
>
>             Hello,
>
>             I have an equation structured like in the attached,
>             however I am unsure of the correct syntax to compute in
>             Scilab.
>
>             One can calculate the first term of the expansion but
>             obvioulsy it needs to go to a large number (approximating
>             infinity eg 20).
>             I am sure this is something very straightforward!
>
>             Any ideas welcome.
>
>             Thanks for the help
>
>             Lester
>
>             att: image of equation, test code
>
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