Re: inputing nothing in a manipulate box
- To: mathgroup at smc.vnet.net
- Subject: [mg101761] Re: inputing nothing in a manipulate box
- From: Simon <simonjtyler at gmail.com>
- Date: Thu, 16 Jul 2009 08:19:53 -0400 (EDT)
- References: <h3kdhk$g72$1@smc.vnet.net>
On Jul 15, 7:11 pm, Lobotomy <labb... at gmail.com> wrote:
> If you have a Manipulate command with a function generating a graph
> and then input nothing there will be an error. nothing=!=0 in this
> case. with nothing i mean, erasing whatever number is there and
> pressing enter without entering 0 or any other number.
>
> how can this be solved? i want that nothing == 0 in my calculations
> when one uses the input box
Hi,
If nothing is entered into the InputField, then it returns Null
The following will check for that
Manipulate[Dynamic@If[x == Null, 0, x], {x, 0, 1}]
Maybe more generally you want to have any non-numeric value changed to
zero, eg
ForceNumber = If[NumericQ@#, #, 0] &;
Manipulate[Graphics[Point[ForceNumber /@ {x, y}], PlotRange -> {{-1,
1}, {-1, 1}}, Frame -> True], {{x, 0}, -1, 1}, {{y, 0}, -1, 1}]
Simon