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MathGroup Archive 2004

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Re: function IF with several equality conditions

  • To: mathgroup at
  • Subject: [mg49111] Re: function IF with several equality conditions
  • From: Bill Rowe <readnewsciv at>
  • Date: Thu, 1 Jul 2004 05:26:16 -0400 (EDT)
  • Sender: owner-wri-mathgroup at

On 6/30/04 at 5:34 AM, mbekkali at (Mukhtar Bekkali) wrote:

>I have two questions that HELP file of Mathematica does not

>(1) How do I implement IF with several conditions.  I tried
>something like this

>a=1; Table[If[{x1>a,x2<a},0,1],{x1,0,2},{x2,0,2}]

>and get no results.

The construct {expr1, expr2 ... } is a list of expressions and doesn't have a true/false value. Change the code to read

Table[If[x1>a && x2<a,0,1],{x1,0,2},{x2,0,2}]



and you will get what you want

>Also, (2) IF does not accept equality conditions either, say

>a=1; Table[If[x=a,0,1],{x,0,2}]

The operator "=" is the assignment operator not a test for equality. You need to use "==" as in


>I am surprised that such simple things are not covered by help

Both of these are covered in the Mathematica Book which is included as part of the Help Browser. But since both the usage of "==" vs "=" and usage of {} to represent lists are fundamental Mathematica syntax, they are not documented again in the documentation for If. 
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