Thanks, but the thing is that I need the zeros as well, and I would like the coefficiets to also be in a specific order that I specify and not according to what maple choses. I have a list to derivatives, e.g. [Uxx Uxy Uyy Ux Uy U] and I would like to check for their appearence on different equations. I need to get back a vector, in this example of length 6, with the coeficients in that specific order (including zeros if the derivative does not appear in the equation).

Thanks!

Uri

Thanks, but the thing is that I need the zeros as well, and I would like the coefficiets to also be in a specific order that I specify and not according to what maple choses. I have a list to derivatives, e.g. [Uxx Uxy Uyy Ux Uy U] and I would like to check for their appearence on different equations. I need to get back a vector, in this example of length 6, with the coeficients in that specific order (including zeros if the derivative does not appear in the equation).

Thanks!

Uri