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Is there a command that takes an equation as an input and creates an output with a list of terms in the original equation? Something like:

Input: Foo[ (1+a) x+ (2.5-b) y^2+ 3 c z^{1.3}]

Output: { (1+a) x ,  (2.5-b) y^2 ,  3 c z^{1.3} }
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You can expand your equation and then apply List. –  Spawn1701D May 16 '13 at 17:32
    
Variables, e.g. Variables[x^3 + 6 x^2 y + 3 x y z + x z^2 + 1] yields {x, y, z} –  Artes May 16 '13 at 17:32
    
If you want monomials there is e.g. MonomialList[a x + b y^2 + 3 c z^{1.3}] yielding {{1. a x, 1. b y^2, 3. c z^(13/10)}} –  Artes May 16 '13 at 17:38
    
Hi guys, thank you very much for your help so far. Unfortunately I have had to update the question as I try your suggestions and see what additional flexibility I else I need. –  DJBunk May 16 '13 at 17:41
1  
So you need List @@ ((1 + a) x + (2.5 - b) y^2 + 3 c z^1.3) returning {(1 + a) x, (2.5 - b) y^2, 3 c z^1.3} –  Artes May 16 '13 at 17:44

2 Answers 2

What you are asking to do, it seems, is to replace the Plus Head, with the List Head. The Apply function, shorthanded as @@, will do what you want:

Input: expr = Foo[a + b + c];

Now we can get just the a+b+c with First:

Input: expr2 = First@expr;

Check out FullForm to get rid of shorthanded notation:

Input: FullForm[expr2]
Output: Plus[a,b,c]

And finally, we can turn Plus into List with Apply:

Input: List@@expr2
Output: {a,b,c}

All in one line:

Input: List@@First[Foo[a+b+c]]
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I am fairly certain that Foo was given as the example of the function itself, meaning that Foo[a + b + c] should directly evaluate to {a, b, c}. Nevertheless +1. –  Mr.Wizard Oct 8 at 16:11

Examining the structure of the expression with TreeForm

TreeForm@Foo[(1 + a) x + (2.5 - b) y^2 + 3 c z^{1.3}]

TreeForm@Foo[(1 + a) x + (2.5 - b) y^2 + 3 c z^{1.3}]

shows us another way:

Level[Foo[(1 + a) x + (2.5 - b) y^2 + 3 c z^{1.3}], {3}]

(* {(1 + a) x, (2.5 - b) y^2, 3 c z^1.3} *)

(Simply count the depth of the function arguments from the Head of the expression.)

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