Re: Why these graphs differ?

*To*: mathgroup at smc.vnet.net*Subject*: [mg33966] Re: [mg33925] Why these graphs differ?*From*: BobHanlon at aol.com*Date*: Wed, 24 Apr 2002 01:23:05 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

In a message dated 4/23/02 8:04:47 AM, vvb at mail.strace.net writes: >These solutions, naturally, coincide. > > DSolve[{y'[z] == z, y[0] == 1}, y[z], z][[1, 1, 2]] >Evaluate[DSolve[{y'[z] == z, y[0] == 1}, y[z], z][[1, 1, 2]]] > >(2 + z^2)/2 >(2 + z^2)/2 > > >But, surprisingly, the corresponding graphs are not identical: > >Plot[ DSolve[{y'[z] == z, y[0] == 1}, y[z], z][[1, 1, 2]], {z, >0, 1}] >Plot[Evaluate[DSolve[{y'[z] == z, y[0] == 1}, y[z], z][[1, 1, 2]]], {z, >0, 1}] > > >Is it a feature or a problem? "Plot evaluates its arguments in a non-standard way (see Section A.4.2). You should use Evaluate to evaluate the function to be plotted if this can safely be done before specific numerical values are supplied. " Bob Hanlon Chantilly, VA USA