Consider the following:
list={1,2,2,2,3};
I would like to replace all 2 with the string "Test". Replace[list,2->"Test"] does not do it.
Result must be: {1,"Test","Test","Test",3}.
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3 Answers
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You can use:
list /. {2 -> "Test"}
(* Out[]:= {1, "Test", "Test", "Test", 3} *)
answered Apr 19, 2012 at 16:45
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3$\begingroup$ Internally,
a /. bbecomesReplaceAll[a,b]which by default, replaces all instances found. $\endgroup$– rcollyerApr 19, 2012 at 17:00 -
$\begingroup$ I prefere this one at the moment, as you can replace different figures at the same time, e.g.
list/.{1->"A",2->"X"}. I wounder whetherReplaceis able of that too? $\endgroup$– JohnApr 19, 2012 at 17:01 -
1$\begingroup$ @John It is:
Replace[list, {1 -> "B", 2 -> "Test"}, {1}]$\endgroup$ Apr 19, 2012 at 17:02 -
2$\begingroup$ @John note, that once a match is found, it stops looking, and refuses to apply a sequence of replacements, e.g.
a /. {a -> b, b -> c}returnsb. But, you can useReplaceRepeated(//.), instead.a //. {a -> b, b -> c}then returnsc. $\endgroup$– rcollyerApr 19, 2012 at 17:05
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Replace by default works on the whole expression. You can add a level specification
list={1,2,2,2,3};
Replace[list,2->"Test", {1}]
Gives
{1, "Test", "Test", "Test", 3}
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For example:
list = {1, 2, 2, 2, 3};
list /. {2 -> "test"}
If[# == 2, "test", #] & /@ list
Replace[list, 2 -> "test", 1]
ReplacePart[list, Position[list, 2] -> "test"]
answered Apr 19, 2012 at 17:01