```Date: Apr 24, 2013 6:16 AM
Author: Bob Hanlon
Subject: Re: cannot work a "conditional If"

Your output of signy is a list of length 1 rather than a number.Consequently, the test in the If does not evaluate as either True or Falseand the If statement returns unevaluated. Change the definition of signy toproduce a number, i.e.,signy[t_] := y[t] /. orbit[[1]]However, rather than use an If statement, I recommend that you usePiecewise.Bob HanlonOn Mon, Apr 22, 2013 at 3:11 AM, <patrice.haldemann@gmail.com> wrote:> Hi everybody>> I am a newcomer in the mathematica world and I have been facing an issue> for some days.>> I have used mathematica to solve an NDSolve and it has worked well>> I have tested  expressions with the solution of NDSolve and its has worked> well.>> Now if I use an expression in an "Conditional If", it does not work.>> Thank you for your help>>> See below>> signy[t_] := y[t] /. orbit   where y[t] is the solution of the NDSolve>> signy[1]>> {-1.96861}>>  ang12[t_] := If[signy[t] > 3, 10, 6]>>  ang12[1]>> If[{-1.96861} > 3, 10, 6]>>
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