Whats the value of B ??

1 次查看（过去 30 天）
mr mo
mr mo 2016-6-10
评论： Walter Roberson 2016-6-10
Hello every one.
I wanna find the value of B, that make the variable Z=0.8 or very close to 0.8. How can I do that in Matlab ?
here is the sample of my code .
n=10;
C=[0.2 0.55 0.7 0.8 0.99 0.1 0.24 0.33 0.44 0.74];
P=exp(-B*C);
P=P/sum(P);
z = sum (P(1 : n/2));
With best regards.

请先登录，再回答此问题。

采纳的回答

Walter Roberson
Walter Roberson 2016-6-10
syms B
n = 10;
C = [0.2 0.55 0.7 0.8 0.99 0.1 0.24 0.33 0.44 0.74];
P = exp(-B.*C);
P2 = P./sum(P);
z = sum(P2(1 : n/2));
Bval = vpasolve(z == 0.8,B);
However, this will give only one of the 89 solutions. It happens to be the only real-valued solution so that might be good enough for you.
  2 个评论
mr mo
mr mo 2016-6-10
Thanks for your help
But I want to use the variable B in the Next other lines of my code, and here the variable B becomes symbolic, How can I use B in other lines ?? with best regards
Walter Roberson
Walter Roberson 2016-6-10
If you construct the other lines symbolically in B then use
subs(expression, B, Bval)
If the other lines expect B numerically, then use
syms Bs
n = 10;
C = [0.2 0.55 0.7 0.8 0.99 0.1 0.24 0.33 0.44 0.74];
P = exp(-Bs.*C);
P2 = P./sum(P);
z = sum(P2(1 : n/2));
B = double( vpasolve(z == 0.8, Bs) );

请先登录，再进行评论。

更多回答（1 个）

Torsten
Torsten 2016-6-10
function main
x0=1;
sol=fzero(@fun,x0)
function y=fun(x)
n=10;
C=[0.2 0.55 0.7 0.8 0.99 0.1 0.24 0.33 0.44 0.74];
for k=1:length(x)
xk=x(k);
P=exp(-xk*C);
P=P/sum(P);
y(k)=0.8-sum(P(1:n/2));
end
Best wishes
Torsten.

类别

在 Help Center 和 File Exchange 中查找有关 Sequence and Numeric Feature Data Workflows 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by