MATLAB: Sub2ind gives error: Error using sub2ind (line 73) Out of range subscript.

sub2indsubscript

Im trying to adapt an existing script to match equivalent data but for a different time period.
The initial code is 
Nfirms      = 50000;
Tperiods    = 1000;
Tshock      = 800;
% pre-allocation;
sim_i_a    = zeros(Nfirms,Tperiods);
sim_i_k    = zeros(Nfirms,Tperiods);
sim_a_val  = zeros(Nfirms,Tperiods);
sim_k_val  = zeros(Nfirms,Tperiods);
sim_c_val  = zeros(Nfirms,Tperiods);
sim_coll_val = zeros(Nfirms,Tperiods);
sim_effective_lambda_val = zeros(Nfirms,Tperiods);
sim_Psi_val = zeros(Nfirms,Tperiods);
sim_i_a(:,1) = index_a0;
sim_i_k(:,1) = index_k0;
sim_a_val(:,1) = a_grid(sim_i_a(:,1));
sim_k_val(:,1) = k_grid(sim_i_k(:,1));
sim_i_r   = zeros(Tperiods,1);
sim_i_r(1:Tshock-1)         = 6;  %until 1993;
sim_i_r(Tshock:Tshock+17)   =[5,...  %1994
                              5,...  %1995
                              5,...  %1996
                              4,...  %1997
                              3,...  %1998
                              1,...  %1999
                              2,...  %2000
                              2,...  %2001
                              1,...  %2002
                              1,...  %2003
                              1,...  %2004
                              1,...  %2005
                              2,...  %2006
                              3,...  %2007
                              2,...  %2008
                              3,...  %2009
                              2,...  %2010
                              2];  %2011
sim_i_r(Tshock+18:end)=2;
And i changed sim_i_r to 
sim_i_r   = zeros(Tperiods,1);
sim_i_r(1:Tshock-1)         = 2;  %until 2011;                
sim_i_r(Tshock:Tshock+6)    =[2,...  %2011
                              0,...  %2012
                              0,...  %2013
                              -1,...  %2014
                              -1,...  %2015
                              -1,...  %2016
                              -1];  %2017
sim_i_r(Tshock+8:end)=-0.1;
But in doing so i get an error with the sub2ind function in the two following instances: 
%generate paths;
it = 2;
index        = sub2ind( size(sim_pol_ind_ap), sim_i_a(:,it-1),sim_i_k(:,it-1),sim_i_zp(:),sim_i_zt(:,it-1),sim_i_r(it-1)*ones(Nfirms,1),sim_i_tau(:,it-1),sim_i_q(:,it-1) );
for it = 2:Tperiods
    sim_i_a(:,it)       = sim_pol_ind_ap( index );
    sim_i_k(:,it)       = sim_pol_ind_kp( index );
    index               = sub2ind( size(c_val), sim_i_a(:,it),sim_i_k(:,it),sim_i_zp(:),sim_i_zt(:,it),sim_i_r(it)*ones(Nfirms,1),sim_i_tau(:,it),sim_i_q(:,it) );
    sim_a_val(:,it)     = a_grid(sim_i_a(:,it));
    sim_k_val(:,it)     = k_grid(sim_i_k(:,it));
    sim_c_val(:,it)     = c_val( index ); 
    sim_coll_val(:,it)  = binding_collateral( index  ); 
    sim_effective_lambda_val(:,it) = effective_lambda(index);
end
Sizes in the first argument of each sub2ind call, respectively, 
size(sim_pol_ind_ap)
ans =
   120   120     2    11     6
size(c_val)
ans =
   120   120     2    11     6
I don't understand why i get this error, since i didn't change the size of the array sim_i_r, just the values it takes at different points.

Best Answer

sim_i_r was valid indices (integers greater than zero), but you changed it to invalid ones (zeros, decimals, negatives). Matlab should give a better warning ("invalid index" vs "index out of range")
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