how do i plot a solved diff eq with coefficients after the diff eq is solved

Hello

This is a post in follow up of discussion I began with user name Bruno, Torsten...

The original problem was this: I am trying to use ode45 to to solve a system of first order linear diff eq They are a set of 4 diff eq X'=AX where X' is a 4x1 column matrix of dx_i/dt where i= 1,2,3 or 4 A is 4x4 matrix of time independent values (ie coefficient values) X is a 4x1 column matrix of x_i(t) where i= 1,2,3 or 4

I am trying to let the x_i's to be activities in compartments of a biological system as a function of time.

This part was accomplished.

Now there are a set of coefficients that I must multiply the activities that were solved for and plot. For example Compartment activity functions were found from the diff eq's: a(1), a(2) a(3) & a(4)

I must multiply the activity functions by the coefficients and plot the new activities. example: 0.5*a(1) + 0.3 * a(2)

Right now I'm just trying to define a new function such that this is possible: b = 0.045 * a(1) + 0.013 * a(3)

Just wanting to get feedback from anyone out there Thanks in advance