MathGroup Archive 2002

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Why these graphs differ?


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


  • Prev by Date: Re: Linking mathematica with VC++6.0
  • Next by Date: invisible graphics
  • Previous by thread: Why these graphs differ?
  • Next by thread: Re: Why these graphs differ?