how can i transfer a variable's value from one function to another?

I want to transfer ther value of Protrusion(i) from function G_yi to function sumin, in other words, I want to use the value of Protrusion(i) in function sumin,like making it a global variable,but when i run the following code,it gave me a message"??? Error: File: sumin.m Line: 1 Column: 30 Unbalanced or misused parentheses or brackets.",I dont know why, if anyone can help, I will appreciate. below are one main code, and 3 function code.

Di=4e-3;
PR=double_int(0,Di,0,Di)

function SS=double_int(innlow,innhi,outlow,outhi)
Protrusion1=outlow;Protrusion2=outhi;Friction1=innlow;Friction2=innhi;
SS=quad(@G_yi,Protrusion1,Protrusion2,[],[],Friction1,Friction2);  

function f=G_yi(Protrusion,Friction1,Friction2)
for i=1:n
f(i)=quad(@sumin,Friction1,Friction2,[],[],Protrusion(i));
end
f=f(:);

function fun=sumin(Friction,Protrusion(i))
MeanShearStress=5 ;   %unit Pa
Density=1e3;
Ustar=sqrt(MeanShearStress/Density);
N=15;
D=zeros(N,1);
p=zeros(N,1);
for k=1:N-1;
    D(1)=0.5e-3;
    p(1)=1/N;
    D(k+1)=D(k)+0.5e-3;
    p(k+1)=p(k);
end;
%p1=1/3, p2=1/3,p3=1/3
%D1=40e-6,D2=60e-6, D3=80e-6 

KinematicViscosity=1.004e-6;
D50=4e-3;
Roughness=2*D50;
RoughnessRenolds=Ustar*Roughness/KinematicViscosity;
if RoughnessRenolds>100
    Intensity=Ustar*2.14;
    Skewness=0.43;
    Flatness=2.88;
else
Intensity=Ustar*(-0.187*log(RoughnessRenolds)+2.93);
Skewness=0.102*log(RoughnessRenolds);
Flatness=0.136*log(RoughnessRenolds)+2.30;
end
CoefficientC=-0.993*log(RoughnessRenolds)+12.36;
 SpecificWeightofSand=1.8836e4;
 SpecificWeightofWater=9.789e3 ; 
Di=4e-3;
% Protrusion=1e-3;
Thickness=1.5*D50;
    Y1=0.25*Thickness;
    Y2(i)=0.25*Thickness+Protrusion(i);

      Sum=zeros(N,1);
  for m=1:N-1
      Kapa=0.4;
      ff1=@(y) (Ustar*CoefficientC.*y/Thickness).*sqrt((0.5*Di)^2-(y-Protrusion(i)-Y1+0.5*Di).^2);
      ff2=@(y) sqrt((0.5*Di)^2-(y-Protrusion(i)-Y1+0.5*Di).^2);
      if Y2(i)<=Thickness
          MeanBedVelocity(i)=quad(ff1,Y1,Y2(i))./(quad(ff2,Y1,Y2(i))); 
      else
          MeanBedVelocity(i)=(quad(ff1,Y1,Thickness)+quad(ff1,Thickness,Y2(i)))./(quad(ff2,Y1,Y2(i)));
      end

      if MeanBedVelocity(i)<=Ustar*CoefficientC
          Yb(i)=(MeanBedVelocity(i)*Thickness)/(Ustar*CoefficientC);
      else
          Yb(i)=Thickness*exp(Kapa*(MeanBedVelocity(i)/Ustar-CoefficientC));
      end;

      ParticleRenolds(i)=MeanBedVelocity(i).*Protrusion(i)/KinematicViscosity;
      if ParticleRenolds(i)<=1754
          Cd(i)=(24./ParticleRenolds(i)).*(1+0.15*ParticleRenolds(i).^0.687);
      else
          Cd(i)=0.36;
      end;

      if ParticleRenolds(i)<8000
          Cl(i)=Cd(i);
       end;
              h1(i)=Yb(i)-Y1-Protrusion(i)+0.5*Di;
              h2=Di*(Friction+0.5*D(m)-0.5*Di)/(Di+D(m));
              Ld(i)=h1(i)+h2;
              Ll=sqrt((0.5*Di)^2-h2.^2);
              Lw=Ll;
              Pei=zeros(N,1);
              Phi=zeros(N,1);
              for j=2:N;
                  Pei(1)=p(1)*Di/(Di+D(1));
                  Pei(j)=p(j)*Di/(Di+D(j))+ Pei(j-1);
                  Phi(j)=1-Pei(j);
              end;
            HidingFactor=(Pei(N)/Phi(N))^0.6;
            EffectiveShearStress=HidingFactor*MeanShearStress;
  %           SpecificWeightofSand=1.8836e4;
  %           SpecificWeightofWater=9.789e3   ; %at 20 degree centigrade
            DimensionlessEffectiveShearStress= EffectiveShearStress/((SpecificWeightofSand-SpecificWeightofWater)*Di); 
            ff3=@(y) sqrt((0.5*Di)^2-(y-Protrusion(i)-Y1+0.5*Di).^2);
            A(i)=quad(ff3,Y1,Y2(i));
            Br=Ustar*sqrt((2*Lw*pi*Di^2)./((Cd(i).*Ld(i)+Cl(i).*Ll)*6.*A(i)*DimensionlessEffectiveShearStress));  % Rolling Threshold   
            Bl=Ustar*sqrt((2*pi*Di^2)/(Cl(i)*6.*A(i)*DimensionlessEffectiveShearStress));  %Lifting Threshold

            %syms Ub  ;   % Instantaneous velocity
  %           U=((Ub-MeanBedVelocity)/Intensity);
            PDF=@(Ub) (exp(-((Ub-MeanBedVelocity)/Intensity).^2/2)/(Intensity*sqrt(2*pi))).*(1+(Skewness/factorial(3))*(((Ub-MeanBedVelocity)/Intensity).^3-3*((Ub-MeanBedVelocity)/Intensity))+(Flatness-3)*(((Ub-MeanBedVelocity)/Intensity).^4-6*((Ub-MeanBedVelocity)/Intensity).^2+3)/factorial(4))/Intensity;  %PDF of Velocity Fluctuation
            Pr(i)=quad(PDF,-Bl,-Br)+quad(PDF,Br,Bl);
  %           Pl=1-quad(PDF,-Bl,Bl);

          %end

               Sum(1)=p(1)*Pr(i);
               Sum(m+1)=p(m)*Pr(i)+Sum(m);
   end;
           fun=Sum(m+1);

Answer 1

[William]

Two methods I use:

1. Use global variables (be careful) use all caps for a variable

global NEW_VARAIBLE;

Or use a "save" command to save data somewhere on your drive and then acess it by using the "load" command

save mydata.mat
load mydata.mat

[Lin LI]

Thank you , Willam, I appreciate your help very much.

Answer 2

[Walter Roberson]

function fun=sumin(Friction,Protrusion(i))

is illegal syntax. The variables on the right hand side of a function declaration must be pure variable names with no indexing, no list construction, no cell referencing, no structure array referencing.

[Fangjun Jiang]

You can define

function fun=sumin(Friction,Protrusion)

and then call it as

sumin(Fr,Pro(i))

[Lin LI]

Thank you very much, Walter, I have changed the code as below. Can this keep the Protrusion(i) consistant in the two functions , by using f(i)=quad(@sumin,Friction1,Friction2,[],[],Protrusion); and

function fun=sumin(Friction,Protrusion,i)? Protrusion now probly is a vector other than a scalar.

Di=4e-3;

PR=double_int(0,Di,0,Di)

function SS=double_int(innlow,innhi,outlow,outhi)

Protrusion1=outlow;Protrusion2=outhi;Friction1=innlow;Friction2=innhi;

SS=quad(@G_yi,Protrusion1,Protrusion2,[],[],Friction1,Friction2);

function f=G_yi(Protrusion,Friction1,Friction2)

for i=1:n

f(i)=quad(@sumin,Friction1,Friction2,[],[],Protrusion);

end

f=f(:);

function fun=sumin(Friction,Protrusion,i)

MeanShearStress=5 ; %unit Pa

Density=1e3;

Ustar=sqrt(MeanShearStress/Density);

N=15;

D=zeros(N,1);

p=zeros(N,1);

for k=1:N-1;

D(1)=0.5e-3;

p(1)=1/N;

D(k+1)=D(k)+0.5e-3;

p(k+1)=p(k);

end;

%p1=1/3, p2=1/3,p3=1/3

%D1=40e-6,D2=60e-6, D3=80e-6

KinematicViscosity=1.004e-6;

D50=4e-3;

Roughness=2*D50;

RoughnessRenolds=Ustar*Roughness/KinematicViscosity;

if RoughnessRenolds>100

Intensity=Ustar*2.14;

Skewness=0.43;

Flatness=2.88;

else

Intensity=Ustar*(-0.187*log(RoughnessRenolds)+2.93);

Skewness=0.102*log(RoughnessRenolds);

Flatness=0.136*log(RoughnessRenolds)+2.30;

end

CoefficientC=-0.993*log(RoughnessRenolds)+12.36;

SpecificWeightofSand=1.8836e4;

SpecificWeightofWater=9.789e3 ;

Di=4e-3;

% Protrusion=1e-3;

Thickness=1.5*D50;

Y1=0.25*Thickness;

Y2(i)=0.25*Thickness+Protrusion(i);

Sum=zeros(N,1);

for m=1:N-1

Kapa=0.4;

ff1=@(y) (Ustar*CoefficientC.*y/Thickness).*sqrt((0.5*Di)^2-(y-Protrusion(i)-Y1+0.5*Di).^2);

ff2=@(y) sqrt((0.5*Di)^2-(y-Protrusion(i)-Y1+0.5*Di).^2);

if Y2(i)<=Thickness

MeanBedVelocity(i)=quad(ff1,Y1,Y2(i))./(quad(ff2,Y1,Y2(i)));

else

MeanBedVelocity(i)=(quad(ff1,Y1,Thickness)+quad(ff1,Thickness,Y2(i)))./(quad(ff2,Y1,Y2(i)));

end if MeanBedVelocity(i)<=Ustar*CoefficientC

Yb(i)=(MeanBedVelocity(i)*Thickness)/(Ustar*CoefficientC);

else

Yb(i)=Thickness*exp(Kapa*(MeanBedVelocity(i)/Ustar-CoefficientC));

end; ParticleRenolds(i)=MeanBedVelocity(i).*Protrusion(i)/KinematicViscosity;

if ParticleRenolds(i)<=1754

Cd(i)=(24./ParticleRenolds(i)).*(1+0.15*ParticleRenolds(i).^0.687);

else

Cd(i)=0.36;

end; if ParticleRenolds(i)<8000

Cl(i)=Cd(i);

end;

h1(i)=Yb(i)-Y1-Protrusion(i)+0.5*Di;

h2=Di*(Friction+0.5*D(m)-0.5*Di)/(Di+D(m));

Ld(i)=h1(i)+h2;

Ll=sqrt((0.5*Di)^2-h2.^2);

Lw=Ll;

Pei=zeros(N,1);

Phi=zeros(N,1);

for j=2:N;

Pei(1)=p(1)*Di/(Di+D(1));

Pei(j)=p(j)*Di/(Di+D(j))+ Pei(j-1);

Phi(j)=1-Pei(j);

end;

HidingFactor=(Pei(N)/Phi(N))^0.6;

EffectiveShearStress=HidingFactor*MeanShearStress;

% SpecificWeightofSand=1.8836e4;

% SpecificWeightofWater=9.789e3 ; %at 20 degree centigrade

DimensionlessEffectiveShearStress= EffectiveShearStress/((SpecificWeightofSand-SpecificWeightofWater)*Di);

ff3=@(y) sqrt((0.5*Di)^2-(y-Protrusion(i)-Y1+0.5*Di).^2);

A(i)=quad(ff3,Y1,Y2(i));

Br=Ustar*sqrt((2*Lw*pi*Di^2)./((Cd(i).*Ld(i)+Cl(i).*Ll)*6.*A(i)*DimensionlessEffectiveShearStress)); % Rolling Threshold

Bl=Ustar*sqrt((2*pi*Di^2)/(Cl(i)*6.*A(i)*DimensionlessEffectiveShearStress)); %Lifting Threshold %syms Ub ; % Instantaneous velocity

% U=((Ub-MeanBedVelocity)/Intensity);

PDF=@(Ub) (exp(-((Ub-MeanBedVelocity)/Intensity).^2/2)/(Intensity*sqrt(2*pi))).*(1+(Skewness/factorial(3))*(((Ub-MeanBedVelocity)/Intensity).^3-3*((Ub-MeanBedVelocity)/Intensity))+(Flatness-3)*(((Ub-MeanBedVelocity)/Intensity).^4-6*((Ub-MeanBedVelocity)/Intensity).^2+3)/factorial(4))/Intensity; %PDF of Velocity Fluctuation

Pr(i)=quad(PDF,-Bl,-Br)+quad(PDF,Br,Bl);

% Pl=1-quad(PDF,-Bl,Bl); %end Sum(1)=p(1)*Pr(i);

Sum(m+1)=p(m)*Pr(i)+Sum(m);

end;

fun=Sum(m+1);consistant

[Lin LI]

Thank you very much,Fangjun and Walter, I have changed the code as above, a new error appears,"??? In an assignment A(I) = B, the number of elements in B and I must be the same.

Error in ==> sumin at 118

Ld(i)=h1(i)+h2;"

how can i fix this problem?

[Fangjun Jiang]

Run "dbstop if error" and then debug your code. h2 might be a non-scalar.

[Lin LI]

yes, fangjun,h2 might be a vector, how can I change it ? i am quite new to matlab, i am trying to learn it as quickly as possible, but still such a lot of things to learn.thank you very much.

[Lin LI]

can i make it he(i)?

[Lin LI]

can i make it h2(i)?