how can i overcome this error

 CCT(2,3,2,3)

 sum =
     0
     0
 Error in RCT3 (line 2)
 syms t r theta phi p(r) q(r) a  

 Output argument "R" (and maybe others) not
 assigned during call to "C:\Users\Shiraz
 Khan\Documents\MATLAB\RCT3.m>RCT3".

 Error in CCT (line 13)
    sum=sum+g(i,m)*RCT3(j,k,l,m);

[Geoff Hayes]

shiraz - can you share the code for RCT3.m? Given the error message, the R output parameter is not being set given your inputs.

[Geoff Hayes]

Shiraz's answer moved here

function [R]= RCT3(i,j,k,m)
syms t r theta phi p(r) q(r) a  
g=[exp(p(r)) 0 0 0; 0 -exp(q(r)) 0 0; 0 0 -r^2 0; 0 0 0 -r^2*(sin(theta))^2];

x= [t r theta phi];
A=diff(SRH2(i,k,m),x(1,j));
% pretty(A)

B=diff(SRH2(i,j,m),x(1,k));
%  pretty(B);
sum1=0;
for n=1:4
    sum1=sum1+SRH2(i,k,n)*SRH2(n,j,m);
end
sum1;
%  pretty(sum1)
sum2=0;
for n=1:4
    sum2=sum2+SRH2(i,j,n)*SRH2(n,k,m);
end
sum2;
%   pretty(sum2)
sum=A-B+sum1-sum2;
sum;
pretty(sum)
end

Answer 1

[Geoff Hayes]

Shiraz - your function signature is

 function [R]= RCT3(i,j,k,m)

which means that the output parameter from your function is named R and so you must initialize a local variable (within your code) with that same name. If you don't do this, then you will get the Output argument "R" (and maybe others) not assigned during call.

Perhaps this is the sum local variable in your code? If it is, then rename it to R. If it isn't, then rename it anyway since it will conflict with the MATLAB built-in function sum.