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MathGroup Archive 2002

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Re: Test of a pure function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg34041] Re: [mg34010] Test of a pure function
  • From: BobHanlon at aol.com
  • Date: Sat, 27 Apr 2002 00:57:14 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 4/26/02 5:11:41 AM, soconnor at ccs.nrl.navy.mil writes:

>I hope someone can help me with this I know the solution should be easy
>but I am still learning how pure functions work.
>
>I am trying to pick out a position in a list were a number falls i.e.
>
>Position[xBins, _?(#1<=x <= #2 &)].  I keep getting errors Like these
>
>
>Function::slotn: Slot number 2 in #1 x #2& cannot be filled
>from \
>(#1 x #2&)[List].
>
>Function::slotn: Slot number 2 in
>#1 x #2& cannot be filled from \
>(#1 x #2&)[-1].
>
>From
>In[83]:=
>Function::slotn: Slot number 2 in #1 x #2& cannot be filled from
>\
>(#1 x #2&)[-0.995].
>
>General::stop: Further output of
>Function::slotn will be suppressed during \
>this calculation.
>
>
>Can I make a comparison with the nth and nth+1 element in a pure function.
>

Rather than trying to compare x to two adjacent values, restructure the 
question to count the number of values less than or equal to x.

myPosition[xBins_?VectorQ, x_?NumericQ] :=
 
    Count[xBins, _?(#<=x&)]+1;

data = Sort[Table[Random[], {10}]]

{0.08812644925276472,
 
  0.10010226701182356,
 
  0.4254438313086471,
 
  0.4540738901849056,
 
  0.5471335846922069,
 
  0.6297724295620055,
 
  0.725499086248874,
 
  0.8527355066955329,
 
  0.8919613144350851,
 
  0.9392439737457312}

myPosition[data, .5]

5


Bob Hanlon
Chantilly, VA  USA


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