Matlab Error "Attempted to access -- ; index out of bounds because numel--=???.

If my code looks like the following;

time=0; %Initialise time

particleno=9

dt=0.01;

tfinal=40;

diagstep=10;

diagcounter=0;

while time<tfinal

tie=time+dt;

   if ((int8(time/diagstep) * diagstep) == int8(time)) 
       [xcounter] = ParticleCounterFun(x0, particleno);   
       diagcounter=diagcounter+1;
   end

 Xtcounter(diagcounter)=xcounter(diagcounter);

end %End while time<tfinal LOOP

the FUNCTION FILE FOR PARTICLECOUNTERFUN IS;

function [ xcounter ] = ParticleCounterFun( x0, particleno )

%Initialise counters used in E field diagnostics

counter01=0;

counter12=0;

counter23=0;

counter34=0;

counter45=0;

for np=1:particleno
     if (0<=x0(np) & x0(np)<1)
         counter01=counter01+1;
     end
     if (1<=x0(np) & x0(np)<2)
         counter12=counter12+1;
     end
     if (2<=x0(np) & x0(np)<3)
         counter23=counter23+1;
     end
     if (3<=x0(np) & x0(np)<4)
         counter34=counter34+1;
     end
     if (4<=x0(np) & x0(np)<5)
         counter45=counter45+1;
     end

end

xcounter=[counter01 counter12 counter23 counter34 counter45];

end

Anyway i get this;

>> ParticlePusher Attempted to access xcounter(6); index out of bounds because numel(xcounter)=5.

Error in ParticlePusher (line 101) Xtcounter(diagcounter)=xcounter(diagcounter);

Help please!

Answer 1

[Shuba Nandini]

Hi Phoebe,

The indexing error occurred because the 'Xtcounter' object is trying to access an element of 'xcounter' that does not exist. The xcounter variable depends on the value of the 'diagcounter' variable, which may have caused the error.

To resolve the indexing error in the code, kindly modify your code as shown below:

% Initialize array to store xcounter values at each diagnostic step
Xtcounter = [];   

while time < tfinal
    time = time + dt; % Update time in each loop
    
    if ((int8(time / diagstep) * diagstep) == int8(time)) 
        xcounter = ParticleCounterFun(x0, particleno);
        % Increment diagnostic counter and store xcounter in Xtcounter
        diagcounter = diagcounter + 1;
        Xtcounter(diagcounter, :) = xcounter;
    end
end

I have modified the code to ensure that each xcounter array is stored as a row in Xtcounter for every diagnostic step, rather than attempting to access individual elements.

I hope the above provided code will help you to resolve the issue!