What changes do I need to make in this code to change from NRZL into NRZI?

clear; close;

bits = [0 1 1 0 1 0 0 1 0 1 1 0 0 1 0 1]; % input bit stream

streamLen = length(bits); % length of the stream positionTime = 0.0001; % position duration

endTime = streamLen - positionTime; % required end time for given bit string

t = 0:positionTime:endTime; j = 1; % index of the signal vector, s bit = 1; % current bit

for i = 0:positionTime:endTime % if (floor(i)+1 ~= bit) % checks whether in the same bit bit = bit + 1; end;

    if (bits(bit) == 0)                     % positive voltage for bit 0
        s(j) = 1;
    else                                    % negative voltage for bit 1
        s(j) = -1;
    end;
    j = j + 1;
end;

plot(t,s); % PLOTTING THE RESULTS axis([0 streamLen -3 3]); xlabel('Signal Element (s)'); ylabel('Voltage');

set(gca, 'XGrid', 'on'); % X-axis grid set(gca, 'XTick', [0:1:streamLen]); % adjust X-axis ticks