Re: Round up a number to 4 decimal positions

I'm apparently missing something. The ROUNDUP function in EXCEL take the
value of .0142 and make it .0142, and the value of .0142000001 will round
up to .0143. If the requirement is to mock the EXCEL ROUNDUP function then
you will need to add .0000999999 or however many nines that are needed
to fill in the rest of the decimal points. 4 zeros followed by all 9s.
That away anything greater than .0142 will be rounded up to .0143

You do not need to use any of the EVAL(H) or %DECH() opcodes/bifs. just
simple math.


On Wed, Mar 20, 2013 at 12:49 PM, John Yeung <gallium.arsenide@xxxxxxxxx>wrote:

Well, adding 0.00005 and then doing a normal round (half-adjust) is
clearly wrong:

If the true value to be rounded happens to be 0.0142 exactly, then
your algorithm produces 0.0143.

The suggestions to add whatever is JUST smaller than 0.00005 and then
round normally; or to add JUST less than 0.0001 and then truncate; are
the right ones.

But what is JUST smaller than 0.00005? It depends on the number of
decimal places in the intermediate result (in this case, the
reciprocal of the rate).

For example, say the rate is exactly 399.999 (I'm using 3 decimal
places because your example rate has 3 decimal places). Then the
reciprocal is slightly higher than 0.0025, and thus should be rounded
up to 0.0026. This is in fact what Excel does, when using the
algorithm you describe.

But if you're doing this in RPG, and you're storing the intermediate
result in (for example) a field with 7 decimal places (and I'm
choosing this because you quoted your example value as 0.0141326),
then you're going to get 0.0025000. If you add just under 0.00005 to
that, you get 0.0025499, and when you round that to 4 places, you'll
only wind up with 0.0025, which is wrong.

(Don't get confused: You don't "fix" that by adding exactly 0.00005
before rounding, as you currently plan to do. If the rate happens to
be exactly 400.000, then the true reciprocal should be 0.0025 and your
method will yield 0.0026.)

Incidentally, your 7-digit intermediate value uses truncation. The
reciprocal of 70.758 is actually closer to 0.0141327 (which you would
get with normal rounding on 7 decimal places).

John


On Wed, Mar 20, 2013 at 12:04 PM, Jeff Young <jyoung0950@xxxxxxxxx> wrote:

All,
The Round Up requirement is based on a formula in an EXCEL worksheet that
was used to compute the value I am using.
In essence, what I am being given is a currency exchange rate that I need
to convert to its reciprocal value as a fixed 11.4 field.
This is then used to convert a value in foreign currency to the native
currency.
Ie; Rate = 70.758
Amount = 396.13
1. I need to convert the 396.13 to the native currency. This is done by
multiplying the 396.13 by 70.758. No problems there.
2. I need to have the rate of 70.758 convert to the 11.4 field and use

that

to extend the value from step 1.
In the EXCEL worksheet, the formula to get the 11.4 field uses the

ROUNDUP

function resulting in .0142. The value without rounding is .0141.
I have taken the suggestion from some of the responses to add .00005 to

the

field and then use Eval(H) to get the result.

Thanks to everyone who responded.

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