I ask for the numerical value and it gives me the expression

14 次查看（过去 30 天）
Mohamed Yassin OUKILA
[EDIT: 20110615 12:27 CDT - reformat - WDR]
function y = Eg(t)
syms s;
%constantes
a=14;
b=15;
c=25;
L=c-b;
r=c;
phi=15;
V=7*7*28;
ro=1000;
RHi=100;
RHb=50;
dRH = RHb-RHi;
nus=0.3;
D=1;
M=8.3*10^(-6);
k=1.7;
Es=200000;
nuc=0.2;
lambda=0.3;
tp=1;
nu = k*(1-exp(-lambda*tp));
%------------------------
D1 = s*Epssa(s)-(s+lambda)*Epssa(s+lambda)/exp(lambda*tp);
Egs = (1/k)*(a-b)*(a+b)*(Es/s)*D1*s*(b^2*(nuc-1)-c^2*(nuc+1))/(4*b^2*(s*Epsf(s)-(s+lambda)*Epsf(s+lambda))+(b-c)*(b+c)*D1*((a^2*(nus+1)-b^2*(nus-1))));
y = ilaplace(Egs, s, t);
when I put E(2), it gives me :
ans =
- (12272724991839681694836231076749009375*gamma(3/10)*ilaplace(1/(s^(3/10)*((6003760639686170723358965455476297*gamma(3/10))/(28035470584169798842553923304161280*s^(3/10)) - (22862411300260886193*gamma(3/10))/(124502499794986393600*s^(13/10)) + 454730688161014190625/(9223372036854775808*s) - (113177415720074643*15^(1/2)*(-375*s)^(3/2))/(368934881474191032320*(-s)^(5/2)) + (26947003742874915*15^(1/2)*(-375*s)^(3/2))/(295147905179352825856*(-s)^(3/2)*s^(3/2)) - (16168202245724949*10^(1/2)*(-375*s)^(3/2))/(295147905179352825856*(-s)^(3/2)*s^(3/2)*exp(10*s^(1/2))) - (33609745164258450522786035802189*15^(1/2)*(-s)^(1/2)*erf(5*s^(1/4)*i)*(-375*s)^(3/2)*i)/(207691874341393105141219853168803840*s^(13/4)*exp(25*s^(1/2))) + (33609745164258450522786035802189*15^(1/2)*(-s)^(1/2)*erf(5*s^(1/4)*i)*(-375*s)^(3/2)*i)/(2076918743413931051412198531688038400*s^(15/4)*exp(25*s^(1/2))) + (33609745164258450522786035802189*15^(1/2)*(-s)^(1/2)*erf(15^(1/2)*s^(1/4)*i)*(-375*s)^(3/2)*i)/(207691874341393105141219853168803840*s^(13/4)*exp(25*s^(1/2))) - (33609745164258450522786035802189*15^(1/2)*(-s)^(1/2)*erf(15^(1/2)*s^(1/4)*i)*(-375*s)^(3/2)*i)/(2076918743413931051412198531688038400*s^(15/4)*exp(25*s^(1/2))))), s, 2))/2978768749568041127021354351067136 + (9346944469561546516875*gamma(3/10)*ilaplace(1/(s^(13/10)*((6003760639686170723358965455476297*gamma(3/10))/(28035470584169798842553923304161280*s^(3/10)) - (22862411300260886193*gamma(3/10))/(124502499794986393600*s^(13/10)) + 454730688161014190625/(9223372036854775808*s) - (113177415720074643*15^(1/2)*(-375*s)^(3/2))/(368934881474191032320*(-s)^(5/2)) + (26947003742874915*15^(1/2)*(-375*s)^(3/2))/(295147905179352825856*(-s)^(3/2)*s^(3/2)) - (16168202245724949*10^(1/2)*(-375*s)^(3/2))/(295147905179352825856*(-s)^(3/2)*s^(3/2)*exp(10*s^(1/2))) - (33609745164258450522786035802189*15^(1/2)*(-s)^(1/2)*erf(5*s^(1/4)*i)*(-375*s)^(3/2)*i)/(207691874341393105141219853168803840*s^(13/4)*exp(25*s^(1/2))) + (33609745164258450522786035802189*15^(1/2)*(-s)^(1/2)*erf(5*s^(1/4)*i)*(-375*s)^(3/2)*i)/(2076918743413931051412198531688038400*s^(15/4)*exp(25*s^(1/2))) + (33609745164258450522786035802189*15^(1/2)*(-s)^(1/2)*erf(15^(1/2)*s^(1/4)*i)*(-375*s)^(3/2)*i)/(207691874341393105141219853168803840*s^(13/4)*exp(25*s^(1/2))) - (33609745164258450522786035802189*15^(1/2)*(-s)^(1/2)*erf(15^(1/2)*s^(1/4)*i)*(-375*s)^(3/2)*i)/(2076918743413931051412198531688038400*s^(15/4)*exp(25*s^(1/2))))), s, 2))/2645678120643460864
:o

请先登录，再回答此问题。

回答（3 个）

Jan
Jan 2011-6-15
I assume "E(2)" is a typo and you mean "Eg(2)". Perhaps this works:
Value = Eg(2);
eval(Value)
Sean de Wolski
Sean de Wolski 2011-6-15
double(ans)
perhaps?
or perhaps
doc subs
for s
Mohamed Yassin OUKILA
[EDIT: 20110616 10:05 CDT - reformat - WDR]
Actually It gives me
??? Error using ==> evalin
Undefined function or variable 's'.
Error in ==> sym.eval at 15
s = evalin('caller',vectorize(map2mat(char(x))));
------------------------
I guess the problem is from a function called Erfi that I have download from Mathworks and It doesn't work with symbols. That's why I can't the "ilaplace". Here is the whole program:
%-------------------------------------
function ans=erfi(x)
% %erfi(x). The Imaginary error function, as it is defined in Mathematica
% %erfi(z)==erf(iz)/i (z could be complex) using
% %the incomplete gamma function in matlab: gammainc
% %Using "@": erfi = @(x) real(-sqrt(-1).*sign(x).*gammainc(-x.^2,1/2))
% %Note: limit(x->0) erfi(x)/x -> 2/sqrt(pi)
%
% %Example 1:
% x=linspace(0.001,6,100);
% y=exp(-x.^2).*erfi(x)./2./x;
% figure(1), clf;plot(x,y*sqrt(pi))
%
% %Example 2:
% [x,y]=meshgrid(linspace(-3,3,180),linspace(-3,3,180));
% z=x+i*y;
% figure(1), clf;contourf(x,y,log(erfi(z)))
% axis equal;axis off
xc=5.7;%cut for asymptotic approximation (when x is real)
ans=~isreal(x).*(-(sqrt(-x.^2)./(x+isreal(x))).*gammainc(-x.^2,1/2))+...
isreal(x).*real(-sqrt(-1).*sign(x).*((x<xc).*gammainc(-x.^2,1/2))+...
(x>=xc).*exp(x.^2)./x/sqrt(pi));
%------------------------------------------------------
%graphe.m
k=1.7;
lambda=0.3;
tp=1;
nu = k*(1-exp(-lambda*tp));
Ec = nu*floor(Eg(t-tp));
%graphe
ezplot(Ec,[1 35])
%----------------------------------------
function ans = Epssa(s)
syms t;
Epsa = -16.7*10^(-6)*t^(0.3);
ans = laplace(Epsa);
%-----------------
function y = Epsf(t)
%constantes
a = 14;
b=15;
c=25;
L=c-b;
r=c;
phi=15;
V=7*7*28;
ro=1000;
RHi=100;
RHb=50;
dRH = RHb-RHi;
nus=0.3;
D=1;
M=8.3*10^(-6);
k=1.7;
Es=200000;
nuc=0.2;
lambda=0.3;
tp=1;
nu = k*(1-exp(-lambda*tp));
%-------------
%RH(c,s)
%Bi
syms s;
B1 = b*sqrt(s)/sqrt(D);
B2 = c*sqrt(s)/sqrt(D);
B3 = r*sqrt(s)/sqrt(D);
B4 = -b*exp(B2)*(b-r)*(b+r)*RHi*sqrt(s)-3*c*exp(B2)*(b-r)*(b+r)*sqrt(s);
B5 = D^(7/4)*sqrt(pi)*dRH*(3*sqrt(D)-2*b*sqrt(s))*sqrt(-s/D)*(erfi(sqrt(b)*(s/D)^(1/4))-erfi(sqrt(r)*(s/D)^(1/4)))/(b^(3/2)*s^(9/4));
RH= sqrt(D)*exp(-c*sqrt(s)/sqrt(D))*(-b*c*s/D)^(3/2)*((D)^(3/2)*sqrt(-b*c*s/D)*(-6*c^(3/2)*(sqrt(6*D)*exp(B1)-exp(B3)*sqrt(D*r))*dRH-B4)/(b^2*c^2*s^2)+B5)/(2*(3*c+b)*s^(3/2));
y = -1.1*M*((c^2-b^2)*RHi/(2*s)-RH);
%--------------------------------------------------
function y = Eg(t)
syms s;
%constantes
a=14;
b=15;
c=25;
L=c-b;
r=c;
phi=15;
V=7*7*28;
ro=1000;
RHi=100;
RHb=50;
dRH = RHb-RHi;
nus=0.3;
D=1;
M=8.3*10^(-6);
k=1.7;
Es=200000;
nuc=0.2;
lambda=0.3;
tp=1;
nu = k*(1-exp(-lambda*tp));
%------------------------
D1 = s*Epssa(s)-(s+lambda)*Epssa(s+lambda)/exp(lambda*tp);
Egs = (1/k)*(a-b)*(a+b)*(Es/s)*D1*s*(b^2*(nuc-1)-c^2*(nuc+1))/(4*b^2*(s*Epsf(s)-(s+lambda)*Epsf(s+lambda))+(b-c)*(b+c)*D1*((a^2*(nus+1)-b^2*(nus-1))))
y = ilaplace(Egs);
%-----------------------------------------
I really appreciate your help guys :)

类别

在 Help Center 和 File Exchange 中查找有关 Calculus 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