MTTGx(i,j) := df(MTTZ(i,1), xj, 1);
  END;
END;

% Find MTTGu;
write "% Find MTTGu;";

IF MTTNu>0 THEN 
BEGIN
matrix MTTGu(MTTNz,MTTNu);
FOR j := 1:MTTNu DO
  BEGIN
  uj := MTTu(j,1);
  FOR i := 1:MTTNz DO
    MTTGu(i,j) := df(MTTZ(i,1), uj, 1);
  END;
END
ELSE
  MTTGu := 0;


%Create E matrices
write "%Create E matrices";

IF MTTNx>0 THEN 
BEGIN
matrix MTTExx(MTTNx,MTTNx); MTTExx := MTTFx*MTTGx;

matrix MTTEyx(MTTNy,MTTNx); MTTEyx := MTTFy*MTTGx;
matrix MTTE(MTTNx,MTTNx);   MTTE := MTTI - MTTExx;
IF MTTNu>0 THEN 
  matrix MTTExu(MTTNx,MTTNu); MTTExu := MTTFx*MTTGu;
END;
END;

IF MTTNu>0 THEN 
  BEGIN
  matrix MTTEyu(MTTNy,MTTNu); MTTEyu := MTTFy*MTTGu;
  END
ELSE
  MTTEyu := 0;




  %% The following gets rid of the dZs; there must be a better way.
  MTTdZ1 := 0;
  MTTdZ2 := 0;

  MTTdZ19 := 0;

IF MTTNx>0 THEN 
BEGIN
MTTEdX := MTTdX; %Ie MTTEdX is MTTdX with the dz terms deleted ie EdX.
MTTdX := MTTdXs;  %Restore the symbolic dX

IF MTTNu>0 THEN 
  %% Add on input derivative terms
  MTTEdX := MTTEdX + MTTExu*MTTdu;
END;

IF MTTNy>0 THEN 
  %% Add on output derivative terms
  MTTEdx := MTTEdX + MTTEyx*(MTTE^(-1))*MTTEdX;
END;
END;


%%%%%MTTY := MTTY + MTTEyx*MTTEdX;
%%% This causes the matrix mismatch
%%% MTTdXs and MTTdu need setting in _def.r file

IF MTTNu>0 THEN 
  MTTY := MTTY +  MTTEyu*MTTdu;
END;

IF MTTNx>0 THEN 
  MTTY := MTTY + MTTEyx*(MTTE^(-1))*MTTEdX;


END; %%of MTTNz>0