Assignment between unlike types is not allowed in matlab structure .pls say something

ERROR :Assignment between unlike types is not allowed in matlab structure .pls say something.the code is as follows.

for i2=1:1:n
    S2(i2).xd=rand(1,1)*xm;
    XR(i2)= S2(i2).xd;
    S2(i2).yd=rand(1,1)*ym;
    YR(i2)=S2(i2).yd;
    S2(i2).type='N';%initially no cluster heads only nodes
    S2(i2).id=i2;
    keep(i2)=i2;
    temp_rnd0=i2;
    %random election of normal nodes
    if(temp_rnd0>=(x+m)*n+1)
        S2(i2).E=Eo;
        S2(i2).ENERGY=0;
    end
     if(temp_rnd0<(x+m)*n+1)&&(temp_rnd0>m*n)
        S2(i2).E=Eo*(1+b);
        S2(i2).ENERGY=0.5;
    end
    if(temp_rnd0<m*n+1)
        S2(i2).E=Eo*(1+a);
        S2(i2).ENERGY=1;
    end 
end

[Jonas]

please explain what your variables are (content, size, type) and where exactly the error occurs (which line of your code)

[Jan]

@Wondimu Bantihun: Whenever you mention an error in the forum, attach a copy of the complete error message. This makes it much easier to help.