Re: Replacing list elements while retaining structure
- To: mathgroup at smc.vnet.net
- Subject: [mg74032] Re: Replacing list elements while retaining structure
- From: "Ray Koopman" <koopman at sfu.ca>
- Date: Wed, 7 Mar 2007 03:07:37 -0500 (EST)
- References: <esdj70$olc$1@smc.vnet.net>
See the thread "Insulating data from code" that ran May 16-23, 2006: http://groups.google.com/group/comp.soft-sys.math.mathematica/browse_frm/thread/6f294d230f9fd211/ D. Grady wrote: > Okay, so I have two lists, X and Y. X has some complex structure > which is important, but the values contained in X are not important. > Y has values that are important, but the structure of Y is not. I was > to sequentially replace all the elements in X with the elements of Y. > > It's assumed that X and Y have the same total number of elements, i.e. > Length[Flatten[X]] == Length[Flatten[Y]] > > Here is an example: > > In[8]:= > structurize[{x,x,{{x},x},x},{1,2,3,4,5}] > > Out[8]= > {1,2,{{3},4},5} > > This is what I have so far: > > structurize[X_List, Y_List] := ReplacePart[X, Flatten[Y], Position[X, > a_ /; \ > (Head[a] =!= List), Heads -> False], > Table[{i}, {i, 1, Length[ > Flatten[Y]]}]] /; Length[Flatten[X]] == Length[Flatten[Y]] > > This works fine so long as the elements of X are atomic expressions; > however, if there is an element of X which is a more complicated > expression, like x^2, then this function does not work as desired > because the pattern in Position[] matches x^2 as well as x and 2. Is > there a way to avoid matching parts of a subexpression? Is there a > better way to approach the problem from the get-go? > > Thanks in advance!