Skip to main content
Mathematica

You are not logged in. Your edit will be placed in a queue until it is peer reviewed.

We welcome edits that make the post easier to understand and more valuable for readers. Because community members review edits, please try to make the post substantially better than how you found it, for example, by fixing grammar or adding additional resources and hyperlinks.

Required fields*

5
  • $\begingroup$ So in your example expr, a b c d e f counts but a d c d e f doesn't? This will be very dependent on how the terms in the expression are arranged. Would you want it to generalise to, for example, picking out terms involving b d e f? $\endgroup$ Commented Oct 31, 2017 at 2:37
  • $\begingroup$ If you're just interested in the literal occurrence of c d e f as a string in the expanded form of expr, and you're not worried about the order depending on Mathematica's canonical ordering, you could use Pick[#, StringContainsQ["c d e f"] /@ ToString /@ #] &@(List @@ Expand@expr). $\endgroup$ Commented Oct 31, 2017 at 2:48
  • 1
    $\begingroup$ @aardvark2012 No, the order does not matter when doing /. Mathematica will match a b or b a for the pattern a b. Compare a b c/.a b->x and a b c/.b a->x they give same answer which is c x. Your string solution will not work, since only a b will be matched and not b a as in the case of general pattern $\endgroup$ Commented Oct 31, 2017 at 2:53
  • 2
    $\begingroup$ As you note, all the time seems to be being spent on Expand (Simplify is even worse). Coefficient[func, c d e f] c d e f returns the same as g and is almost order of magnitude faster when they're both passed already Expanded (or Simplifyed) expressions (and marginally faster when the argument isn't pre-Expanded, but there's not a lot to choose between them). $\endgroup$ Commented Oct 31, 2017 at 4:05
  • $\begingroup$ @aardvark2012 thanks for your solution; unfortunatly it also uses Expand, thus its as fast/slow as my original solution. Also it gives a slightly different result, as it also returns expressions like b c d e f^2 which I do not want. $\endgroup$ Commented Oct 31, 2017 at 12:06