Modelling of difference of a constant number and a variable in cvx

hello. I want to model theGP following term in cvx , but it shows error.
(100-p1(t)).I1(t);
that I1(t),p1(t)) are variables. and error is
Error using .
(line 173)
Disciplined convex programming error:
Cannot perform the operation: {concave} .* {log-affine}

Error in project (line 91)
(pl-p1(t)).*I1(t);
please help me.

I suggest you carefully read the chapter on Geometric Programming in the CVX User Guide http://cvxr.com/cvx/doc/gp.html . If you have read it, you have not understood it.

You’ll notice that the chapter includes a link to the tutorial on Geometric Programming at http://web.stanford.edu/~boyd/papers/pdf/gp_tutorial.pdf . I suggest you study that. The tutorial is not as terse as the CVX chapter.

thanks for your answer.