Formatting Decimals

Hello List.

Probably an easy question, but I am not able to format a number to
round up from 3 numbers after the decimal to just 2.

My code looks like this:

$newprice = "$".number_format($old_price, 2, ".", ",");

and this returns "$0.109" when I am looking for "$0.11".


I tried:

$newprice = "$".round(number_format($old_price, 2, ".", ","),2);
But no luck.

Any help is appreciated.

Thanks,

--Rick



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Re: Formatting Decimals

Testing this out a little:

mattias@mumin:~$ php -r 'echo "\$".number_format(0.109, 2, ".", ",")."\n";'
$0.11
mattias@mumin:~$ php -r 'echo "$".number_format(0.109, 2, ".", ",")."\n";'
$0.11
mattias@mumin:~$ php -r 'echo "$".number_format("0.109", 2, ".",
",")."\n";'
$0.11

I think the $ should be escaped with a backslash when enclosed within
double quotes, but even the second and third tries return the correct
result for me. Using PHP 5.2.10.

Cheers,

Mattias

Rick Dwyer wrote:
> Hello List.
>
> Probably an easy question, but I am not able to format a number to
> round up from 3 numbers after the decimal to just 2.
>
> My code looks like this:
>
> $newprice = "$".number_format($old_price, 2, ".", ",");
>
> and this returns "$0.109" when I am looking for "$0.11".
>
>
> I tried:
>
> $newprice = "$".round(number_format($old_price, 2, ".", ","),2);
> But no luck.
>
> Any help is appreciated.
>
> Thanks,
>
> --Rick
>
>
>


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Re: Formatting Decimals

--0016e68ee0394b1283047ce591e2
Content-Type: text/plain; charset=ISO-8859-1

$newprice = sprintf("$%.2f", 15.109);

On Sun, Jan 10, 2010 at 8:36 PM, Rick Dwyer wrote:

> Hello List.
>
> Probably an easy question, but I am not able to format a number to round up
> from 3 numbers after the decimal to just 2.
>
> My code looks like this:
>
> $newprice = "$".number_format($old_price, 2, ".", ",");
>
> and this returns "$0.109" when I am looking for "$0.11".
>
>
> I tried:
>
> $newprice = "$".round(number_format($old_price, 2, ".", ","),2);
> But no luck.
>
> Any help is appreciated.
>
> Thanks,
>
> --Rick
>
>
>
> --
> PHP General Mailing List (http://www.php.net/)
> To unsubscribe, visit: http://www.php.net/unsub.php
>
>

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Re: Formatting Decimals

I have been asked to further modify the value to the nearest half cent.

So if the 3rd decimal spot ends in 1 or 2, it gets rounded down to 0
If it ends in 3, 4, 5, 6 it gets rounded to 5. And if it 7, 8 or 9 it
gets rounded up to full cents.

Can this be done fairly easily? Not knowing PHP well, I am not aware
of the logic to configure this accordingly.

Thanks,
--Rick




On Jan 11, 2010, at 10:55 AM, Ryan Sun wrote:

> $newprice = sprintf("$%.2f", 15.109);
>
> On Sun, Jan 10, 2010 at 8:36 PM, Rick Dwyer
> wrote:
> Hello List.
>
> Probably an easy question, but I am not able to format a number to
> round up from 3 numbers after the decimal to just 2.
>
> My code looks like this:
>
> $newprice = "$".number_format($old_price, 2, ".", ",");
>
> and this returns "$0.109" when I am looking for "$0.11".
>
>
> I tried:
>
> $newprice = "$".round(number_format($old_price, 2, ".", ","),2);
> But no luck.
>
> Any help is appreciated.
>
> Thanks,
>
> --Rick
>
>
>
> --
> PHP General Mailing List (http://www.php.net/)
> To unsubscribe, visit: http://www.php.net/unsub.php
>
>


--Rick



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Re: Formatting Decimals

On Mon, Jan 11, 2010 at 02:55:33PM -0500, Rick Dwyer wrote:

> I have been asked to further modify the value to the nearest half cent.
>
> So if the 3rd decimal spot ends in 1 or 2, it gets rounded down to 0
> If it ends in 3, 4, 5, 6 it gets rounded to 5. And if it 7, 8 or 9 it
> gets rounded up to full cents.
>
> Can this be done fairly easily? Not knowing PHP well, I am not aware
> of the logic to configure this accordingly.

Yes, this can be done, but you'll need to write a function to do it
yourself. I'd also suggest you look into the BCMath functions, at:

http://us2.php.net/manual/en/book.bc.php

Paul

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Re: Formatting Decimals

At 2:55 PM -0500 1/11/10, Rick Dwyer wrote:
>I have been asked to further modify the value to the nearest half cent.
>
>So if the 3rd decimal spot ends in 1 or 2, it gets rounded down to 0
>If it ends in 3, 4, 5, 6 it gets rounded to 5. And if it 7, 8 or 9
>it gets rounded up to full cents.
>
>Can this be done fairly easily? Not knowing PHP well, I am not
>aware of the logic to configure this accordingly.
>
>Thanks,
>--Rick


--Rick:

The above described rounding algorithm introduces more bias than
simply using PHP's round() function, which always rounds down. IMO,
modifying rounding is not worth the effort.

The "best" rounding algorithm is to look at the last digit and do this:

0 -- no rounding needed.
1-4 round down.
6-9 round up.

In the case of 5, then look to the number that precedes it -- if it
is even, then round up and if it is odd, then round down -- or vise
versa, it doesn't make any difference as long as you are consistent.

Here are some examples:

122.4 <-- round down (122)
122.6 <-- round up (123)
122.5 <-- round up (123)

123.4 <-- round down (123)
123.6 <-- round up (124)
123.5 <-- round down (123)

There are people who claim that there's no difference, or are at odds
with this method, but they simply have not investigated the problem
sufficiently to see the bias that rounding up/down causes. However,
that difference is very insignificant and can only be seen after tens
of thousands iterations. PHP's rounding function is quite sufficient.

Cheers,

tedd

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Re: Formatting Decimals

On Jan 11, 2010, at 4:56 PM, tedd wrote:

> At 2:55 PM -0500 1/11/10, Rick Dwyer wrote:
>> I have been asked to further modify the value to the nearest half
>> cent.
>>
>> So if the 3rd decimal spot ends in 1 or 2, it gets rounded down to 0
>> If it ends in 3, 4, 5, 6 it gets rounded to 5. And if it 7, 8 or 9
>> it gets rounded up to full cents.
>>
>> Can this be done fairly easily? Not knowing PHP well, I am not
>> aware of the logic to configure this accordingly.
>>
>> Thanks,
>> --Rick
>
>
> --Rick:
>
> The above described rounding algorithm introduces more bias than
> simply using PHP's round() function, which always rounds down. IMO,
> modifying rounding is not worth the effort.

I understand what you are saying and I agree. But the decision to
round to half cents as outlined above is a client requirement, not
mine (I did try to talk them out of it but no luck).

I come from an LDML environment, not a PHP one so I don't know the
actual code to make this happen. But the logic would be something like:

If 3 decimal than look at decimal in position 3.

If value = 1 or 2 set it to 0
If value = 3,4,5,6 round it to 5
If value = 7,8,9 round it to a full cent


Anybody have specific code examples to make this happen?

Thanks,

--Rick






>
> The "best" rounding algorithm is to look at the last digit and do
> this:
>
> 0 -- no rounding needed.
> 1-4 round down.
> 6-9 round up.
>
> In the case of 5, then look to the number that precedes it -- if it
> is even, then round up and if it is odd, then round down -- or vise
> versa, it doesn't make any difference as long as you are consistent.
>
> Here are some examples:
>
> 122.4 <-- round down (122)
> 122.6 <-- round up (123)
> 122.5 <-- round up (123)
>
> 123.4 <-- round down (123)
> 123.6 <-- round up (124)
> 123.5 <-- round down (123)
>
> There are people who claim that there's no difference, or are at
> odds with this method, but they simply have not investigated the
> problem sufficiently to see the bias that rounding up/down causes.
> However, that difference is very insignificant and can only be seen
> after tens of thousands iterations. PHP's rounding function is
> quite sufficient.
>
> Cheers,
>
> tedd
>
> --
> -------
> http://sperling.com http://ancientstones.com http://earthstones.com
>
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> To unsubscribe, visit: http://www.php.net/unsub.php
>


--Rick



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Re: Formatting Decimals

tedd wrote:
> At 2:55 PM -0500 1/11/10, Rick Dwyer wrote:
>> I have been asked to further modify the value to the nearest half cent.
>>
>> So if the 3rd decimal spot ends in 1 or 2, it gets rounded down to 0
>> If it ends in 3, 4, 5, 6 it gets rounded to 5. And if it 7, 8 or 9
>> it gets rounded up to full cents.
>>
>> Can this be done fairly easily? Not knowing PHP well, I am not aware
>> of the logic to configure this accordingly.
>>
>> Thanks,
>> --Rick
>
>
> --Rick:
>
> The above described rounding algorithm introduces more bias than
> simply using PHP's round() function, which always rounds down. IMO,
> modifying rounding is not worth the effort.
>
> The "best" rounding algorithm is to look at the last digit and do this:
>
> 0 -- no rounding needed.
> 1-4 round down.
> 6-9 round up.
>
> In the case of 5, then look to the number that precedes it -- if it is
> even, then round up and if it is odd, then round down -- or vise
> versa, it doesn't make any difference as long as you are consistent.
>
> Here are some examples:
>
> 122.4 <-- round down (122)
> 122.6 <-- round up (123)
> 122.5 <-- round up (123)
>
> 123.4 <-- round down (123)
> 123.6 <-- round up (124)
> 123.5 <-- round down (123)
>
> There are people who claim that there's no difference, or are at odds
> with this method, but they simply have not investigated the problem
> sufficiently to see the bias that rounding up/down causes. However,
> that difference is very insignificant and can only be seen after tens
> of thousands iterations. PHP's rounding function is quite sufficient.
>
> Cheers,
>
> tedd
>

However that's not what Rick is asking for. He needs a function that
rounds to the half penny with a bias to rounding up (greedy bosses):


Actual Rounded Diff
..011 .010 -.001
..012 .010 -.002
..013 .015 +.002
..014 .015 +.001
..015 .015 .000
..016 .015 -.001
..017 .020 +.003
..018 .020 +.002
..019 .020 +.001
..020 .020 .000
Bias +.005

This could easily be implemented by getting the 3rd decimal and using it
in a switch() statement.

An unbiased system could look like:

Actual Rounded Diff
..011 .010 -.001
..012 .010 -.002
..013 .015 +.002
..014 .015 +.001
..015 .015 .000
..016 .015 -.001
..017 .020 -.002
..018 .020 +.002
..019 .020 +.001
..020 .020 .000
Bias .000

The only difference is the case where the third decimal is 7.

Cheers,

Mattias

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Re: Formatting Decimals

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Content-Type: text/plain; charset=ISO-8859-1

On Mon, Jan 11, 2010 at 7:45 PM, Mattias Thorslund wrote:

> tedd wrote:
>
>> At 2:55 PM -0500 1/11/10, Rick Dwyer wrote:
>>
>>> I have been asked to further modify the value to the nearest half cent.
>>>
>>> So if the 3rd decimal spot ends in 1 or 2, it gets rounded down to 0
>>> If it ends in 3, 4, 5, 6 it gets rounded to 5. And if it 7, 8 or 9 it
>>> gets rounded up to full cents.
>>>
>>> Can this be done fairly easily? Not knowing PHP well, I am not aware of
>>> the logic to configure this accordingly.
>>>
>>> Thanks,
>>> --Rick
>>>
>>
>>
>> --Rick:
>>
>> The above described rounding algorithm introduces more bias than simply
>> using PHP's round() function, which always rounds down. IMO, modifying
>> rounding is not worth the effort.
>>
>> The "best" rounding algorithm is to look at the last digit and do this:
>>
>> 0 -- no rounding needed.
>> 1-4 round down.
>> 6-9 round up.
>>
>> In the case of 5, then look to the number that precedes it -- if it is
>> even, then round up and if it is odd, then round down -- or vise versa, it
>> doesn't make any difference as long as you are consistent.
>>
>> Here are some examples:
>>
>> 122.4 <-- round down (122)
>> 122.6 <-- round up (123)
>> 122.5 <-- round up (123)
>>
>> 123.4 <-- round down (123)
>> 123.6 <-- round up (124)
>> 123.5 <-- round down (123)
>>
>> There are people who claim that there's no difference, or are at odds with
>> this method, but they simply have not investigated the problem sufficiently
>> to see the bias that rounding up/down causes. However, that difference is
>> very insignificant and can only be seen after tens of thousands iterations.
>> PHP's rounding function is quite sufficient.
>>
>> Cheers,
>>
>> tedd
>>
>>
> However that's not what Rick is asking for. He needs a function that rounds
> to the half penny with a bias to rounding up (greedy bosses):
>
>
> Actual Rounded Diff
> .011 .010 -.001
> .012 .010 -.002
> .013 .015 +.002
> .014 .015 +.001
> .015 .015 .000
> .016 .015 -.001
> .017 .020 +.003
> .018 .020 +.002
> .019 .020 +.001
> .020 .020 .000
> Bias +.005
>
> This could easily be implemented by getting the 3rd decimal and using it in
> a switch() statement.
>
> An unbiased system could look like:
>
> Actual Rounded Diff
> .011 .010 -.001
> .012 .010 -.002
> .013 .015 +.002
> .014 .015 +.001
> .015 .015 .000
> .016 .015 -.001
> .017 .020 -.002
> .018 .020 +.002
> .019 .020 +.001
> .020 .020 .000
> Bias .000
>
> The only difference is the case where the third decimal is 7.
>
> Cheers,
>
> Mattias
>
>
> --
> PHP General Mailing List (http://www.php.net/)
> To unsubscribe, visit: http://www.php.net/unsub.php
>
>
Here you go, Rick. Just send the check in the mail ;)

function round_to_half_cent($amount)
{
if (!is_numeric($amount)) throw new Exception('The amount received by the
"round_to_half_cent" function was not numeric');
$parts = explode('.', str_replace(',', '', (string)$amount));
if (count($parts) >= 3) throw new Exception('The amount received by the
"round_to_half_cent" function had too many decimals.');
if (count($parts) == 1)
{
return $amount;
}
$digit = substr($parts[1], 2, 1);
if ($digit == 0 || $digit == 1 || $digit == 2)
{
$digit = 0;
}
elseif ($digit == 3 || $digit == 4 || $digit == 5 || $digit == 6)
{
$digit = .005;
}
elseif ($digit == 7 || $digit == 8 || $digit == 9)
{
$digit = .01;
}
else
{
throw new Exception('OK, perhaps we are talking about different types of
numbers :( Check the input to the "round_to_half_cent" function.');
}
return (double)($parts[0].'.'.substr($parts[1], 0, 2)) + $digit;
}

echo "5.002 = ".round_to_half_cent(5.002);
echo "
70,000.126 = ".round_to_half_cent("70000.126");
echo "
55.897 = ".round_to_half_cent(55.897);
// should cause exception
echo "
One hundred = ".round_to_half_cent("One hundred");

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--0016e6d77d123f8f89047cef667a--

Re: Formatting Decimals

On Mon, Jan 11, 2010 at 04:56:03PM -0500, tedd wrote:

>
> --Rick:
>
> The above described rounding algorithm introduces more bias than
> simply using PHP's round() function, which always rounds down. IMO,
> modifying rounding is not worth the effort.
>
> The "best" rounding algorithm is to look at the last digit and do this:
>
> 0 -- no rounding needed.
> 1-4 round down.
> 6-9 round up.
>
> In the case of 5, then look to the number that precedes it -- if it
> is even, then round up and if it is odd, then round down -- or vise
> versa, it doesn't make any difference as long as you are consistent.
>
> Here are some examples:
>
> 122.4 <-- round down (122)
> 122.6 <-- round up (123)
> 122.5 <-- round up (123)
>
> 123.4 <-- round down (123)
> 123.6 <-- round up (124)
> 123.5 <-- round down (123)
>
> There are people who claim that there's no difference, or are at odds
> with this method, but they simply have not investigated the problem
> sufficiently to see the bias that rounding up/down causes. However,
> that difference is very insignificant and can only be seen after tens
> of thousands iterations. PHP's rounding function is quite sufficient.

This is called (among other things) "banker's rounding". But PHP's
round() function won't do banker's rounding, as far as I know.

Paul

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Re: Formatting Decimals Further Help

Hello List.

In an earlier post, I received help with a custom function to round
decimals off (the custom function provided by Adam Richardson is below).

However in my MySQL db, when I have values with only 1 decimal point,
I need the value PHP returns to display as 2. For example, 3.8 needs
to display as 3.80.

My line of code that calls the custom function looks like this:

$my_price = round_to_half_cent(number_format($my_price, 3, '.', ','));

When the value of $my_price is 3.81, it returns 3.81. However, when
the value of $my_price is 3.8 that is what it returns.

How can I force the formatting of my_price to always contain either 2
or 3 decimal points (3 if the original number contains 3 or more
decimal points to begin with)


Thanks,

--Rick



On Jan 11, 2010, at 10:39 PM, Adam Richardson wrote:

> On Mon, Jan 11, 2010 at 7:45 PM, Mattias Thorslund > >wrote:
>
>> tedd wrote:
>>
>>> At 2:55 PM -0500 1/11/10, Rick Dwyer wrote:
>>>
>>>> I have been asked to further modify the value to the nearest half
>>>> cent.
>>>>
>>>> So if the 3rd decimal spot ends in 1 or 2, it gets rounded down
>>>> to 0
>>>> If it ends in 3, 4, 5, 6 it gets rounded to 5. And if it 7, 8 or
>>>> 9 it
>>>> gets rounded up to full cents.
>>>>
>>>> Can this be done fairly easily? Not knowing PHP well, I am not
>>>> aware of
>>>> the logic to configure this accordingly.
>>>>
>>>> Thanks,
>>>> --Rick
>>>>
>>>
>>>
>>> --Rick:
>>>
>>> The above described rounding algorithm introduces more bias than
>>> simply
>>> using PHP's round() function, which always rounds down. IMO,
>>> modifying
>>> rounding is not worth the effort.
>>>
>>> The "best" rounding algorithm is to look at the last digit and do
>>> this:
>>>
>>> 0 -- no rounding needed.
>>> 1-4 round down.
>>> 6-9 round up.
>>>
>>> In the case of 5, then look to the number that precedes it -- if
>>> it is
>>> even, then round up and if it is odd, then round down -- or vise
>>> versa, it
>>> doesn't make any difference as long as you are consistent.
>>>
>>> Here are some examples:
>>>
>>> 122.4 <-- round down (122)
>>> 122.6 <-- round up (123)
>>> 122.5 <-- round up (123)
>>>
>>> 123.4 <-- round down (123)
>>> 123.6 <-- round up (124)
>>> 123.5 <-- round down (123)
>>>
>>> There are people who claim that there's no difference, or are at
>>> odds with
>>> this method, but they simply have not investigated the problem
>>> sufficiently
>>> to see the bias that rounding up/down causes. However, that
>>> difference is
>>> very insignificant and can only be seen after tens of thousands
>>> iterations.
>>> PHP's rounding function is quite sufficient.
>>>
>>> Cheers,
>>>
>>> tedd
>>>
>>>
>> However that's not what Rick is asking for. He needs a function
>> that rounds
>> to the half penny with a bias to rounding up (greedy bosses):
>>
>>
>> Actual Rounded Diff
>> .011 .010 -.001
>> .012 .010 -.002
>> .013 .015 +.002
>> .014 .015 +.001
>> .015 .015 .000
>> .016 .015 -.001
>> .017 .020 +.003
>> .018 .020 +.002
>> .019 .020 +.001
>> .020 .020 .000
>> Bias +.005
>>
>> This could easily be implemented by getting the 3rd decimal and
>> using it in
>> a switch() statement.
>>
>> An unbiased system could look like:
>>
>> Actual Rounded Diff
>> .011 .010 -.001
>> .012 .010 -.002
>> .013 .015 +.002
>> .014 .015 +.001
>> .015 .015 .000
>> .016 .015 -.001
>> .017 .020 -.002
>> .018 .020 +.002
>> .019 .020 +.001
>> .020 .020 .000
>> Bias .000
>>
>> The only difference is the case where the third decimal is 7.
>>
>> Cheers,
>>
>> Mattias
>>
>>
>> --
>> PHP General Mailing List (http://www.php.net/)
>> To unsubscribe, visit: http://www.php.net/unsub.php
>>
>>
> Here you go, Rick. Just send the check in the mail ;)
>
> function round_to_half_cent($amount)
> {
> if (!is_numeric($amount)) throw new Exception('The amount received
> by the
> "round_to_half_cent" function was not numeric');
> $parts = explode('.', str_replace(',', '', (string)$amount));
> if (count($parts) >= 3) throw new Exception('The amount received by
> the
> "round_to_half_cent" function had too many decimals.');
> if (count($parts) == 1)
> {
> return $amount;
> }
> $digit = substr($parts[1], 2, 1);
> if ($digit == 0 || $digit == 1 || $digit == 2)
> {
> $digit = 0;
> }
> elseif ($digit == 3 || $digit == 4 || $digit == 5 || $digit == 6)
> {
> $digit = .005;
> }
> elseif ($digit == 7 || $digit == 8 || $digit == 9)
> {
> $digit = .01;
> }
> else
> {
> throw new Exception('OK, perhaps we are talking about different
> types of
> numbers :( Check the input to the "round_to_half_cent" function.');
> }
> return (double)($parts[0].'.'.substr($parts[1], 0, 2)) + $digit;
> }
>
> echo "5.002 = ".round_to_half_cent(5.002);
> echo "
70,000.126 = ".round_to_half_cent("70000.126");
> echo "
55.897 = ".round_to_half_cent(55.897);
> // should cause exception
> echo "
One hundred = ".round_to_half_cent("One hundred");
>
> --
> Nephtali: PHP web framework that functions beautifully
> http://nephtaliproject.com


--Rick



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Re: Formatting Decimals Further Help

>Hello List.
>
>In an earlier post, I received help with a custom function to round
>decimals off (the custom function provided by Adam Richardson is
>below).
>
>However in my MySQL db, when I have values with only 1 decimal
>point, I need the value PHP returns to display as 2. For example,
>3.8 needs to display as 3.80.
>
>My line of code that calls the custom function looks like this:
>
>$my_price = round_to_half_cent(number_format($my_price, 3, '.', ','));
>
>When the value of $my_price is 3.81, it returns 3.81. However, when
>the value of $my_price is 3.8 that is what it returns.
>
>How can I force the formatting of my_price to always contain either
>2 or 3 decimal points (3 if the original number contains 3 or more
>decimal points to begin with)
>
>
>Thanks,
>
>--Rick


Rick:

Okay so 3.8 is stored in the database and not as 3.80 -- but that's
not a problem. What you have is a display problem so use one of the
many PHP functions to display numbers and don't worry about how it's
stored.

Cheers,

tedd

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Re: Formatting Decimals Further Help

On Jan 22, 2010, at 4:24 PM, tedd wrote:

>> Hello List.
>>
>> In an earlier post, I received help with a custom function to round
>> decimals off (the custom function provided by Adam Richardson is
>> below).
>>
>> However in my MySQL db, when I have values with only 1 decimal
>> point, I need the value PHP returns to display as 2. For example,
>> 3.8 needs to display as 3.80.
>>
>> My line of code that calls the custom function looks like this:
>>
>> $my_price = round_to_half_cent(number_format($my_price, 3, '.',
>> ','));
>>
>> When the value of $my_price is 3.81, it returns 3.81. However,
>> when the value of $my_price is 3.8 that is what it returns.
>>
>> How can I force the formatting of my_price to always contain either
>> 2 or 3 decimal points (3 if the original number contains 3 or more
>> decimal points to begin with)
>>
>>
>> Thanks,
>>
>> --Rick
>
>
> Rick:
>
> Okay so 3.8 is stored in the database and not as 3.80 -- but that's
> not a problem. What you have is a display problem so use one of the
> many PHP functions to display numbers and don't worry about how it's
> stored.


Hi Ted.

This is exactly what I am trying to do, some of the values in the DB
are going to have 3 decimals, some 2 and some 1.

On my page I pull the value from the db with:

$my_price = $row['my_price'];

This returns 3.80... even though my db has it as 3.8. No problem.
But once I run the variable $my_price through the following line of
code, it is truncating the 0:

$my_price = round_to_half_cent(number_format($my_price, 3, '.', ','));

Again, the above call to the custom function works fine for 2 and 3
decimal points.... just not 1 decimal point. Because I call this
function over many pages, I would prefer if possible to fix it at the
custom function level rather than recode each page. But I will do
whatever is necessary. I afraid with my current understanding of PHP
I am not able to successfully modify the custom function to tack on a
0 when the decimal place is empty. Will keep trying and post if I am
successful

Thanks,

--Rick




I'm afraid with my current understanding of PHP, I am not able to come
up with the logic to

--Rick



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Re: Formatting Decimals

Paul M Foster wrote:
> On Mon, Jan 11, 2010 at 04:56:03PM -0500, tedd wrote:
>
>> --Rick:
>>
>> The above described rounding algorithm introduces more bias than
>> simply using PHP's round() function, which always rounds down. IMO,
>> modifying rounding is not worth the effort.
>>
>> The "best" rounding algorithm is to look at the last digit and do this:
>>
>> 0 -- no rounding needed.
>> 1-4 round down.
>> 6-9 round up.
>>
>> In the case of 5, then look to the number that precedes it -- if it
>> is even, then round up and if it is odd, then round down -- or vise
>> versa, it doesn't make any difference as long as you are consistent.
>>
>> Here are some examples:
>>
>> 122.4 <-- round down (122)
>> 122.6 <-- round up (123)
>> 122.5 <-- round up (123)
>>
>> 123.4 <-- round down (123)
>> 123.6 <-- round up (124)
>> 123.5 <-- round down (123)
>>
>> There are people who claim that there's no difference, or are at odds
>> with this method, but they simply have not investigated the problem
>> sufficiently to see the bias that rounding up/down causes. However,
>> that difference is very insignificant and can only be seen after tens
>> of thousands iterations. PHP's rounding function is quite sufficient.
>
> This is called (among other things) "banker's rounding". But PHP's
> round() function won't do banker's rounding, as far as I know.
>
> Paul
>

floor( $val + 0.5 );

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Re: Formatting Decimals Further Help

Rick Dwyer wrote:
>
> On Jan 22, 2010, at 4:24 PM, tedd wrote:
>
>>> Hello List.
>>>
>>> In an earlier post, I received help with a custom function to round
>>> decimals off (the custom function provided by Adam Richardson is below).
>>>
>>> However in my MySQL db, when I have values with only 1 decimal point,
>>> I need the value PHP returns to display as 2. For example, 3.8 needs
>>> to display as 3.80.
>>>
>>> My line of code that calls the custom function looks like this:
>>>
>>> $my_price = round_to_half_cent(number_format($my_price, 3, '.', ','));
>>>

your doing the number format before the rounding.. here's a version of
the function that should fit the bill:

function round_to_half_cent( $value )
{
$value *= 100;
if( $value == (int)$value || $value < ((int)$value)+0.3 ) {
return number_format( (int)$value/100 , 2);
} else if($value > ((int)$value)+0.6) {
return number_format( (int)++$value/100 , 2);
}
return number_format( 0.005+(int)$value/100 , 3);
}


echo round_to_half_cent( 12.1 ); // 12.10
echo round_to_half_cent( 12.103 ); // 12.105
echo round_to_half_cent( 12.107 ); // 12.11
echo round_to_half_cent( 123456.789 ); // 123,456.79



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Re: Formatting Decimals Further Help

On Jan 22, 2010, at 7:30 PM, Nathan Rixham wrote:


Thanks Nathan I'll give it a shot.

--Rick


>>>>
>
> your doing the number format before the rounding.. here's a version of
> the function that should fit the bill:
>
> function round_to_half_cent( $value )
> {
> $value *= 100;
> if( $value == (int)$value || $value < ((int)$value)+0.3 ) {
> return number_format( (int)$value/100 , 2);
> } else if($value > ((int)$value)+0.6) {
> return number_format( (int)++$value/100 , 2);
> }
> return number_format( 0.005+(int)$value/100 , 3);
> }
>
>
> echo round_to_half_cent( 12.1 ); // 12.10
> echo round_to_half_cent( 12.103 ); // 12.105
> echo round_to_half_cent( 12.107 ); // 12.11
> echo round_to_half_cent( 123456.789 ); // 123,456.79
>
>






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Re: Formatting Decimals Further Help

Rick Dwyer wrote:
> On Jan 22, 2010, at 7:30 PM, Nathan Rixham wrote:
> Thanks Nathan I'll give it a shot.
>

np - here's a more condensed version:

function round_to_half_cent( $value )
{
$value = ($value*100) + 0.3;
$out = number_format( floor($value)/100 , 2 );
return $out . ($value > .5+(int)$value ? '5' : '');
}

>>
>> echo round_to_half_cent( 12.1 ); // 12.10
>> echo round_to_half_cent( 12.103 ); // 12.105
>> echo round_to_half_cent( 12.107 ); // 12.11
>> echo round_to_half_cent( 123456.789 ); // 123,456.79
>>

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Re: Formatting Decimals Further Help

Thank you Nathan,
This worked quite well.
--Rick

On Jan 22, 2010, at 8:10 PM, Nathan Rixham wrote:

> Rick Dwyer wrote:
>> On Jan 22, 2010, at 7:30 PM, Nathan Rixham wrote:
>> Thanks Nathan I'll give it a shot.
>>
>
> np - here's a more condensed version:
>
> function round_to_half_cent( $value )
> {
> $value = ($value*100) + 0.3;
> $out = number_format( floor($value)/100 , 2 );
> return $out . ($value > .5+(int)$value ? '5' : '');
> }
>
>>>
>>> echo round_to_half_cent( 12.1 ); // 12.10
>>> echo round_to_half_cent( 12.103 ); // 12.105
>>> echo round_to_half_cent( 12.107 ); // 12.11
>>> echo round_to_half_cent( 123456.789 ); // 123,456.79
>>>
>
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>






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