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Dear all,

Ngene always raport error when there is "%" in my design.

This doesn't work.

Code: Select all

Design
;alts = alt1, alt2,SQ
;rows = 12
;block=2
;eff = (mnl,d)
;model:
U(SQ) = b1[(n,0.74,0.3)]+ b2[(n,-0.1,0.03)] * F.ref[0] + b3[(n,0.4,0.2)] * P.ref[0]+   b4[(n,0.1,0.05)] *Surf.ref[0]  +  b5[(n,0.2,0.1)]  *  v[0,1] + b6[(n,-0.05,0.02)] * price.ref[0]   + i1[(n,-0.1,0.02)]*F*P  /

U(alt1) =          b2 * F.piv[0,2,4]       + b3 * P.piv[0,500,1000]+        b4[(n,0.1,0.05)] *Surf.piv[-10%,0%,10%]  +  b5 *  v      + b6 * price.piv[-15%,-10%,-5%,0,5%,10%]  + i1*F*P  /

U(alt1) =            b2 * F.piv[0,2,4]      + b3 * P.piv[0,500,1000]+         b4[(n,0.1,0.05)] *Surf.piv[-10%,0%,10%]  +  b5 *  v     + b6 * price.piv[-15%,-10%,-5%,0,5%,10%]  + i1*F*P  $


But after I remove all "%", then it works well:

Code: Select all

Design
;alts = alt1, alt2,SQ
;rows = 12
;block=2
;eff = (mnl,d)
;model:

U(SQ) = b1[(n,0.74,0.3)]+ b2[(n,-0.1,0.03)] * F.ref[0] + b3[(n,0.4,0.2)] * P.ref[0]+ b4[(n,0.1,0.05)] *Surf.ref[0]  +  b5[(n,0.2,0.1)]  *  v[0,1] + b6[(n,-0.05,0.02)] * price.ref[0]+ i1[(n,-0.1,0.02)]*DisF*DisP  /

U(alt1) =                           b2 * F.piv[0,2,4] + b3 * P.piv[0,0.5,1]+ b4[(n,0.1,0.05)] *Surf.piv[-0.1,0,0.1]  +  b5 *  v + b6 * price.piv[-0.15,-0.1,-0.05,0,0.05,0.1]+i1*DisF*DisP  /
U(alt2) =                           b2 * F.piv[0,2,4] + b3 * P.piv[0,0.5,1]+ b4[(n,0.1,0.05)] *Surf.piv[-0.1,0,0.1]  +  b5 *  v + b6 * price.piv[-0.15,-0.1,-0.05,0,0.05,0.1]+i1*DisF*DisP  $

Could anyone tell me why?


And if my reference point is always 0, is it necessary to do a pivot design?

Thank you!
Nice weekend!

Your reference level is 0, so your pivot levels of [-10%,0%,10%] are [0,0,0]. Clearly, you cannot have all zeros as levels for your design. You can only apply a percentage if the reference level is non-zero. Otherwise, you can apply absolute pivots as you have done, for example [-1,0,1].

If your reference level is always zero, then it is not necessary to use pivots. You can also done something like:

Code: Select all

U(SQ) = b1+ b2 * F[0] + b3 * P[0]+   b4 *Surf[0]  +  b5  *  v[0,1] + b6 * price[0]   + i1*F*P  /
U(alt1) =  b2 * F2[0,2,4] + b3 * P2[0,500,1000] + b4 *Surf2[-1,0,1]  +  b5 *  v  + b6 * price2[-1,0,1]  + i1*F*P 

Thank you.