need to solve this matlab function code will only output rows of zeros should have real numbers

1 function [rvec, fvec]=PredatorPrey_1_fcn(parameters, initconds, timedata) 2 % Copy and paste your code here Nm 7 GRR=parameters (1); 5 EFR=parameters(2); 6 GRF=parameters(3); ERF=parameters(4); 8 rinit1=initconds (1); 9 finit1=initconds (2); 00 11 tinit=timedata(1); 12 tfinal=timedata (2); 13 delt=timedata (3); 15 t=tinit:delt:tfinal; rvec=zeros(length(t),1); 17 fvec=zeros(length(t),1); 19 for i=1: length(t)-1 rvec(i+1)=rvec(i) +GRR*rvec(i)-EFR*fvec(i)*rvec(i); fvec(i+1)=fvec(i)+GRF*fvec(i) +ERF*rvec(i)*fvec(i); 22 end