I am getting error "not enough input arguments" , I don't know how to resolve this.

function [dn]=numparticles(t, n)

global SECT funcall No m

funcall=funcall+1;
dn=zeros(SECT,1);
sums=zeros(3,1);


    disp(['Function call ', num2str(funcall),' t value ', num2str(t) ,' of ',num2str(120),'.'])

for i=1:SECT   
   if (i-2 >= 1)
        for j=1:i-2
          sums(1)=sums(1)+beta(i-1,j)*2^(j+1-i)*n(j);
        end
   end
   if (i-1 >= 1)
         for j=1:i-1
           sums(2)=sums(2)+beta(i,j)*2^(j-i)*n(j);
         end
         dn(i)=dn(i)+ n(i-1)*sum(1)+ 0.5*beta(i-1,i-1)*n(i-1)^2-n(i)*sums(2);
   end 
   if (i+1 <=SECT)
%        	dn(i)=dn(i)+2*gamma(i+1)*n(i+1);
        for j=1:SECT
             sums(3)=sums(3)+beta(i,j)*n(j);
        end
        dn(i)=dn(i)-n(i)*sums(3);
   end   
   dn(i)=dn(i)/No(1); 
   
   sums=zeros(3,1);
end

[Jan]

Whenever you mention an error in the forum, post the complete message. It is hard to guess, in which line your code fails, but you have this valuable information directly on the screen. So please share it with the readers.

Is beta a function or an array?

Answer 1

[Jan]

How do you call this function? If you use the green triangle in the editor, the function is called without inputs and you will see the mentioned error.

You have to call it with inputs from the command window or from another script or function:

t = ???;
n = ???;
dn = numparticles(t, n)

[KAJAL KUMARI]

I am using this numparticles in another code which is dn.m

global SECT funcall m No 
relerr=1e-5;
funcall=0;
massinput = 8; %total mass of solid (kg)
d0= 0.2e-3; %particle diameter (m)
densp = 2500; %particle density (kg/m3)
Vo = pi/6*d0^3; %particle volume
massofone = densp*Vo; %mass of one particle (density*volume)
startnum= massinput/massofone; %Initial N naught
SECT = 7; % Number of sections
m=1;
No=zeros(SECT,1);
No(1)=startnum;
[t, N]=ode15s('numparticles',[0 120],No);
%%
% Plots the
figure
for ii=1:size(N)
 plot(1:SECT,N(ii,:),'r');
 xlabel('No. of Sections');
 ylabel('No. of Particles');
 pause(3/100);
end

function  [dn]=numparticles (t, n)

global SECT funcall No m

funcall=funcall+1;
dn=zeros(SECT,1);
sums=zeros(3,1);
 disp(['Function call ', num2str(funcall),' t value ', num2str(t) ,' of',num2str(120),'.'])
for i=1:SECT
     if (i-2 >= 1)
         for j=1:i-2
             sums(1)=sums(1)+beta(i-1,j)*2^(j+1-i)*n(j);
         end
     end
 if (i-1 >= 1)
      for j=1:i-1
           sums(2)=sums(2)+beta(i,j)*2^(j-i)*n(j);
      end
 dn(i)=dn(i)+ n(i-1)*sum(1)+ 0.5*beta(i-1,i-1)*n(i-1)^2-n(i)*sums(2);
 end
 if (i+1 <=SECT)
% dn(i)=dn(i)+2*gamma(i+1)*n(i+1);
      for j=1:SECT
           sums(3)=sums(3)+beta(i,j)*n(j);
      end
 dn(i)=dn(i)-n(i)*sums(3);
 end
 dn(i)=dn(i)/No(1);
 sums=zeros(3,1);
end


function B=beta(i,j)
beta0 = 1; %initial guess
 B = beta0.*1/4.*(2+((i/j)^(1/3))+((j/i)^(1/3))); %brownian motion kernel 
end							
end

[Jan]

If I change the line:

[t, N]=ode15s('numparticles',[0 120],No);

to

[t, N]=ode15s(@numparticles,[0 120],No);

the code runs in Matlab r2021a.

A small acceleration of the code:

function B = beta(i,j)
k = (i/j) ^ (1/3); 
B = 0.25 * (2 + k + 1/k)
end							

[KAJAL KUMARI]

thank you so much, now it is working