# Sigma Notation in Dynare

Hello:

I am a Beginner at Dynare and I am being asked to write the non-linearized New Keynesian Model as described in Walsh(2010) in order for Dynare to run log-linearization. I can’t find how to express the following equation

pstar_t/P_t = {sum_j(0:inf)[w^ibeta^iC_t+i^(1-sigma)phi_t+i(P_t+i/P_t)^theta] / sum_j(0:inf)[w^ibeta^iC_t+i^(1-sigma)*(P_t+i/P_t)^(theta-1)]} *(theta/(theta-1))

Where w and beta are parameters in the interval (0,1), sigma is an aversion risk coefficient and theta is a elasticity, where all of them are given values. pstar_t denotes the optimal price set by firms able to do so at period t, P_t is the aggregate price level at time t, C_t is consumption at time t and phi_t is marginal cost at time t. Sum_i(0:inf)…] denotes the sum, for i gooing from zero to infinity of the expression contained in square brackets. As is notices, there is sigma notation which, as I know, cannot be written down like that in dynare.

Can you please give me indications about how I should input this in dynare?