# Decimal Increment Constaints

I'm using XLSForm. Is there a way to constrain a decimal input field to
only accept increments of 0.5? So, a valid input would be 2.0 or 2.5 but
not 2.75. I'd rather not use calculate to round the decimal (the field that
I'm trying to constrain is collecting the number of stories in a building
and only whole or half stories are possible).

Thanks!

Hi Ed,
You might be able to use the "mod" operator. For example, try something
like this in your constraint column:
(\${floors} mod 0.5) < 0.01 (the 0.01 is to avoid floating point rounding
errors)
However, I've never tested the mod operator in Collect, much less with
decimal values, so I'm not sure if that approach will work.
If it doesn't you can accomplish the same thing with the div operator and
round/int function:
(\${floors} div 0.5) - int(\${floors} div 0.5) < 0.01
Regards,
-Nathan

··· On Saturday, May 11, 2013 9:45:43 AM UTC-7, Ed FitzGerald wrote: > > I'm using XLSForm. Is there a way to constrain a decimal input field to > only accept increments of 0.5? So, a valid input would be 2.0 or 2.5 but > not 2.75. I'd rather not use calculate to round the decimal (the field that > I'm trying to constrain is collecting the number of stories in a building > and only whole or half stories are possible). > > Thanks! >

Thanks for your help Nathan! "Mod" seems to be working in Enketo. I'll test
it out on a device when I get a chance.

··· On Saturday, May 11, 2013 11:47:52 PM UTC-5, Nathan wrote: > > Hi Ed, > You might be able to use the "mod" operator. For example, try something > like this in your constraint column: > (\${floors} mod 0.5) < 0.01 (the 0.01 is to avoid floating point rounding > errors) > However, I've never tested the mod operator in Collect, much less with > decimal values, so I'm not sure if that approach will work. > If it doesn't you can accomplish the same thing with the div operator and > round/int function: > (\${floors} div 0.5) - int(\${floors} div 0.5) < 0.01 > Regards, > -Nathan > > On Saturday, May 11, 2013 9:45:43 AM UTC-7, Ed FitzGerald wrote: >> >> I'm using XLSForm. Is there a way to constrain a decimal input field to >> only accept increments of 0.5? So, a valid input would be 2.0 or 2.5 but >> not 2.75. I'd rather not use calculate to round the decimal (the field that >> I'm trying to constrain is collecting the number of stories in a building >> and only whole or half stories are possible). >> >> Thanks! >> >

Ed,

If the mod trick fails, you can also use regex to match the input.

I haven't tested this extensively, but this should work: [1]+.[0,5]\$

Yaw

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On Sun, May 12, 2013 at 8:25 AM, Ed FitzGerald fitzed@gmail.com wrote:

Thanks for your help Nathan! "Mod" seems to be working in Enketo. I'll test
it out on a device when I get a chance.

On Saturday, May 11, 2013 11:47:52 PM UTC-5, Nathan wrote:

Hi Ed,
You might be able to use the "mod" operator. For example, try something
like this in your constraint column:
(\${floors} mod 0.5) < 0.01 (the 0.01 is to avoid floating point rounding
errors)
However, I've never tested the mod operator in Collect, much less with
decimal values, so I'm not sure if that approach will work.
If it doesn't you can accomplish the same thing with the div operator and
round/int function:
(\${floors} div 0.5) - int(\${floors} div 0.5) < 0.01
Regards,
-Nathan

On Saturday, May 11, 2013 9:45:43 AM UTC-7, Ed FitzGerald wrote:

I'm using XLSForm. Is there a way to constrain a decimal input field to
only accept increments of 0.5? So, a valid input would be 2.0 or 2.5 but not
2.75. I'd rather not use calculate to round the decimal (the field that I'm
trying to constrain is collecting the number of stories in a building and
only whole or half stories are possible).

Thanks!

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