Rounding

PaulowniaK

I'm not able to disclose application details, but let's just say, the said behaviour already exists. The trouble is how I would go about explaining what it's doing to the users. Writing in the Help that "it rounds to the nearest integer" or "it rounds to the nearest 100" automatically suggests it does this:

1.4 turns into 1.
1.5 turns into 2.
1.6 turns into 2.

140 turns into 100.
150 turns into 200.
160 turns into 200.

etc. etc.

which isn't what happens. Sure, I can explain this long hand, but I just wanted to know if there was a proper terminology to explain this.

Almost, but not quite, entirely unlike... me...

Steve Wellens

How's this: Round to one significant digit.

Jorgen Andersson

Rounding to one significant digit.

Wrong is evil and must be defeated. - Jeff Ello[^]

Lost User

http://en.wikipedia.org/wiki/Rounding[^] "Round half down to nearest integral multiplier power of 10"

Peter Wasser "The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts." - Bertrand Russell

Agent__007

:thumbsup: Considering he needs 160.6 to be rounded to 200 and not 161.

Whether I think I can, or think I can't, I am always bloody right!

BillWoodruff

how I would go about explaining what it's doing to the users.

If you owe us money, we get more; if we owe you money, you get less.

“I have diligently numbered the days of pure and genuine happiness which have fallen to my lot: They amount to 14.” Abd-Ar Rahman III, Caliph of Cordoba, circa 950CE.

JMK NI

This is standard rounding The irony is that people are so used to bankers rounding they get confused when they see ordinary rounding, but this is the kind you probably learned about in school! Disregard, I'm an idiot

DaveAuld

Smells very much like "Significant Number Rounding"... http://en.wikipedia.org/wiki/Significant_figures[^] Demo Calculator -> http://ostermiller.org/calc/significant_figures.html[^]

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DaveAuld

JMK-NI wrote:

This is standard rounding

No it isn't. There is a huge difference between standard rounding and significant rounding. There are also many different types of rounding scheme depending on the application: http://en.wikipedia.org/wiki/Rounding[^]

Dave Find Me On:Web|Facebook|Twitter|LinkedIn Folding Stats: Team CodeProject

JMK NI

Well knock me down! It's 6:30AM, I haven't had coffee yet!

PaulowniaK

OK, bad example...

123 would be 120.
125 would be 120.
126 would be 130.

etc. etc.

The point not being the number of significant digits you end up with, but the fact that the rounding is happening at 5 and 6 rather than the more usual 4 and 5.

Almost, but not quite, entirely unlike... me...

DaveAuld · Well knock me down! It's 6:30AM, I haven't had coffee yet!

Well it's now 6:43am, my first meeting with my supervisory team was an hour ago and I have already spoken with my boss onshore, so the day is well underway. Only another 14 or 15 hours still to go. :doh: Feeling :zzz: already.

Dave Find Me On:Web|Facebook|Twitter|LinkedIn Folding Stats: Team CodeProject

PaulowniaK

My understanding of rounding to N significant figure is like this:

1234 to 3 significant figures = 1230
1235 to 3 significant figures = 1240
1236 to 3 significant figures = 1240

The trouble is, I need

1234 to 3 significant figures = 1230
1235 to 3 significant figures = 1230
1236 to 3 significant figures = 1240

The point is, rather than rounding up or down depending on whether the N+1th digit is 4 or 5, but whether it is 5 or 6.

Almost, but not quite, entirely unlike... me...

DaveAuld

Sounds like you want to do Round Half Down + Significant then.

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DaveAuld

Round half down + Significant.

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Agent__007

How about "N Significant Half-Down Rounding[^]"?

Whether I think I can, or think I can't, I am always bloody right!

Jorgen Andersson

So depending on how you want to treat negative numbers you want either "Significant digits round half down" or "Significant digits round half towards zero".

Wrong is evil and must be defeated. - Jeff Ello[^]

Jorgen Andersson

See my other answer, or Daves.

Wrong is evil and must be defeated. - Jeff Ello[^]

PaulowniaK

Cheers. I think "round half down" is the term I needed. :thumbsup:

Almost, but not quite, entirely unlike... me...

PaulowniaK

All values are positive, due to the nature of the application. "Round half down" was the term I was looking for. Thanks for your help. :cool:

Almost, but not quite, entirely unlike... me...