??? Undefined function or method 'gammainc' for input arguments of type 'sym'.

[EDIT: 20110629 09:24 CDT - reformat - WDR]

I found a function here in mathworks called Erfi that i have to use it in a program. however, as I understood, this function doesn't work for s as symbolic . however, i need to do ilaplace for a function that uses it...

here is the error

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??? Undefined function or method 'gammainc' for input arguments of type
'sym'.

Error in ==> erfi1 at 19
ans=~isreal(t).*(-(sqrt(-t.^2)./(t+isreal(t))).*gammainc(-t.^2,1/2))+...

Error in ==> Epsf at 31
        B5 =
        D.^(7./4)*sqrt(pi)*dRH*(3*sqrt(D)-2*b*sqrt(s))*sqrt(-s./D)*(erfi1(sqrt(b)*(s./D).^(1./4))-erfi1(sqrt(r)*(s./D).^(1./4)))./(b.^(3./2)*s.^(9./4));

Error in ==> Egs at 25
y =
(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))));
Error in ==> Eg at 3
y = ilaplace(Egs(s),s,t);

Error in ==> graphe at 6
Ec = nu*Eg(t-tp);  

-------------

and here is the code

---------------

    k=1.7;
    lambda=0.3;
    tp=1;
  nu = k*(1-exp(-lambda*tp));
  t  = 5:35;
  Ec = nu*Eg(t-tp);
  %graphe
  plot(t,Ec)

------------------

function ans=erfi1(t)
% %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)
it says that here is the error !
ans=~isreal(t).*(-(sqrt(-t.^2)./(t+isreal(t))).*gammainc(-t.^2,1/2))+...
  isreal(t).*real(-sqrt(-1).*sign(t).*((t<xc).*gammainc(-t.^2,1/2))+...
  (t>=xc).*exp(t.^2)./t/sqrt(pi));

------------------------

function y = Epsf(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));
%-------------
%RH(c,s)
  %Bi

        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)*(erfi1(sqrt(b)*(s./D).^(1./4))-erfi1(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 = Egs(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);
y = (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))));

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function y = Eg(t)
syms s;
y = ilaplace(Egs(s),s,t);

--------------------------------

function ans = Epssa(s)
syms t;
ans = laplace(Epsa(t),t,s);

-------------------------------

function y = Epsa(t)
y = -16.7*10.^(-6)*t.^(0.3);

--------------------------------

I really appreciate your help because I spent a lot of time in this issue :)

Answer 1

[Walter Roberson]

See <http://www.mathworks.com/support/solutions/en/data/1-4TW73U/index.html?product=SM&solution=1-4TW73U>