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Re: Re: Replace specific element with specific value.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg99732] Re: [mg99679] Re: Replace specific element with specific value.
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Tue, 12 May 2009 03:11:01 -0400 (EDT)
  • Reply-to: hanlonr at cox.net

myReplacePart[data_List, pos_List, parts_List] :=
 
 Module[{newList = data},
   ( newList = ReplacePart[newList, #[[1]] -> #[[2]]]) & /@
    
    Transpose[{Thread[{pos, 2}], parts}];
   newList] /; Length[pos] == Length[parts]

data = {{0, 2}, {2, 3}, {3, 4}, {4, 6}, {6, 8}, {8, 9}, {9, 10}};

positionList = {3, 6, 7};

replacementList = {8, 17, 25};

myReplacePart[data, positionList, replacementList]

{{0, 2}, {2, 3}, {3, 8}, {4, 6}, {6, 8}, {8, 17}, {9, 25}}


Bob Hanlon

---- nick.maj at mssm.edu wrote: 

=============
Thank you all for the replies.

Bill, you are right. To manually input the replacement rules is fine
for only a view variables. For simplicity I kept my example short.
However, I am dealing with quite large lists (100+), so a functional/
programatical approach is necessary. Also, I used characters for
clarity.

Rule @@@ (ToExpression[{#, # <> "+" <> # <> #}] & /@ {"1", "2", "3"})

gives: {1 -> 12, 2 -> 24, 3 -> 36}

Let me elaborate on this problem again with numbers only.

data = {{0, 2}, {2, 3}, {3, 4}, {4, 6}, {6, 8}, {8, 9}, {9, 10}}

positionList = {3, 6, 7}

replacementList = {8, 17, 25}

needed output:

{{0, 2}, {2, 3}, {3, 8}, {4, 6}, {6, 8}, {8, 17}, {9, 25}}

Based on the positionList - replacementList information, the function
must replace the 2nd element in the 3rd, 6th and 7th list of data with
the value 8, 17 and 25 respectively.

I experimented with MapThread[ReplacePart ... but without success.

Thanks in advance, Nick.




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