如何限制待估参数取值范围

请问下各路大神，我想做如下方程的极大似然估计，怎么限制算出来的p的取值范围在0-1之间？ ----------------------- copy starting from the next line ----------------------- * Example generated by -dataex-. To install: ssc install dataex function f = gmmreg2(para,num,X,y ) b=para(1:5); mu1=para(6); mu2=para(7); sig1=para(8); sig2=para(9); p=para(10); eta=y-X*b; pdf=p*normpdf(eta,mu1,sig1)+(1-p)*normpdf(eta,mu2,sig2); pdf=max(pdf,eps); if num==1     f=log(pdf);     else     f=-sum(log(pdf)); end [color=rgb(51, 102, 153) !important]复制代码 ------------------ copy up to and including the previous line ------------------