p1=r1^x1*b^(-r1)/a1 (1) 我想进行泊松分布的参数的非线形回归,p1已知,a1是x1的阶乘,b是自然对数,求r1.如果象(1)那样写,就提示no coefficients specified. p1=c+r1^x1*b^(-r1)/a1 (2) p1=c*r1^x1*b^(-r1)/a1 (3) 如果象(2) (3)那样写,就提示index missing for coefficient c 完全忘了,请达人教教我啊!!!!!!!!!