Don't know if this was usefule to anyone, but it worked ok for my app.
It basically 'normalizes' the
number in e-notation and rounds to the specified number of decimals
of the above format then returns the float result.
static float Rounder(float in, int nDigits)
{
double mult = 1;
String inStr = String.valueOf(in);
int exp = (int) Math.log10(in);
mult = Math.pow(10,-exp + nDigits + 1);
float i = (float) (Math.round(in * mult) / mult);
return(i);
}
On 12/23/2011 11:49 AM, Lee Studley wrote:
> On 12/23/2011 11:29 AM, Michael Büsch wrote:
>> On Thu, 22 Dec 2011 15:16:59 +0100
>> Michael Büsch<[email protected]> wrote:
>>
>>> On Thu, 22 Dec 2011 07:40:19 -0600
>>> Jeff Epler<[email protected]> wrote:
>>>
>>>> I understand the rest, but what's the + 0.1 part doing?
> Curiously I was working on a similar issue using Java. I'm processing a
> database of capacitors and resistors and converting them to enotation
> then back and ran into rounding issues.
>
> Here's an ugly attempt that's not fully tested, but gives the idea:
> ndigits are the number of non-zero digits: I'll post a the final version
> if interested.
> I want to specify the number if sig digits I want for a fractional value:
>
> //ex. 0.000000470266543763 9.21k 9210
> static float Rounder(float in, int nDigits)
> {
> double mult = 1;
> int len = 1;
> String inStr = String.valueOf(in); //converts the input float
> to a string enotation is automatically used if needed.
> String strTemp1 = inStr; // todo was going to split the string
> to further process.
>
> len = inStr.length(); // not used
> int exp = (int) Math.log10(in); // grab the exponent for
> creating a x10 power multiplier to 'normalize' the value for us
> mult = Math.pow(10,-exp + nDigits + 1);
>
> //
> float i = (float) (Math.round(in * mult) / mult);
> return(i);
> }
>
>
>>> The +0.1 is to protect against floating point inaccuracies.
>>> Imagine the ceil() operation yields a 200.0, for example. But
>>> due to floating point inaccuracies it's actually represented
>>> as 199.9999999999999. So the (implicit) int cast would (tail)-cast
>>> it to 199, instead of the correct 200. The +0.1 avoids that.
>>>
>>>> fwiw the code was added to fix this bug:
>>>> http://sourceforge.net/tracker/?func=detail&aid=2478266&group_id=6744&atid=106744
>>>>
>>>> I think that ceil, round or (implicit in integer division) floor are all
>>>> OK as fixes to the original problem, so I'd be tempted to just drop the
>>>> useless ceil() call instead and leave the behavior unchanged.
>>> Ok, well. I'm don't really understand the code good enough to have an
>>> opinion on this, but changing the code to this:
>>>
>>> servo_mult = traj_period_nsec / nsec;
>>>
>>> should maintain the current semantics, but avoid the floating point stuff.
>>>
>>> Please also note that some older compilers are confused by that floating
>>> point stuff there and throw internal errors. (That's how I got attracted
>>> to that code). So it should be fixed either way.
>> Should I resend the patch, or are you going to apply that manually?
>>
>
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