function out=constant(x)
%This function takes in an array of measurements and returns calculated
%equilibrium constant for the gas phase reaction
%The values of x are as follows:
%
%x(1); Water concentration
%x(2); Nitrogen concentration
%x(3); Nitrous oxide concentration
%x(4); Hydrogen concentration
water=x(:,1);
nitrogen=x(:,2);
noxide = x(:,3);
hydrogen=x(:,4);
%Let's calculate the equilibrium constant.
%K = [N2]*[H2O]^2 / [NO]^2*[H2]^2

K = nitrogen.*water.^2./(noxide.^2.*hydrogen.^2);
%Return the value of K
out = K;