Roundto() seems inconsistent

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1

HI

For the community members better educated in maths than me, should the answer in row 4 not be -200?

image

Regards
Piet

2

Come to think of it, shouldn’t the answer for row 1 be 136?

3

There’s three formulas for rounding: RoundUp(), RoundDown(), & RoundTo(). RoundTo will go to the nearest integer. So maybe try using one of the other two to get your desired result?

4

This works exactly as intended. It rounds to the nearest value that is a multiple of your factor.

Row 1 it round to the nearest of 134 or 135.,
Row 2 it round to the nearest of 130 or 140,
Row 3 it round to the nearest of -130 or -135,
Row 4 it round to the nearest of -100 or -200,
Row 5 it round to the nearest of -130 or -140

5

For sake of completeness, there are actually 8 Rounding-related formulas in Coda and they all behave in slightly different ways. The Coda School covers each of the 8 rounding formulas in length here

For the sake of simplicity, Standard rounding rules state that anything BELOW 5 will round down and anything ABOVE 5 will round up.

Heres some examples with standard rounding rules

  • 4.9 to the factor of 10 will round → 0

    • 4.9 is below the 5 threshold so it will round DOWN based on standard rounding rules. But if you were rounding 5 to the factor of 10, it will round UP to 10.

  • 4.9 to the factor of 1 will round → 5

    • In this case, we are comparing the numbers after the decimal to determine which way our number will go. So 0.9 is above the 0.5 threshold with a factor of 1, so it will round up. BUT 4.49 rounding to the factor of 1 is BELOW the 0.5 threshold so it would round DOWN to 4.

  • 1.49 to the factor of 1 will round → 1

  • 1.499 to the factor of 1 will round → 1

  • 1.5 to the factor of 1 will round → 2

  • 49 to the factor of 100 → 0

  • 50 to the factor of 100 → 100

Round and RoundTo are essentially equivalent in that they follow standard rounding rules, but RoundTo allows you to define a factor.

RoundUp and RoundDown though do NOT follow standard rounding rules. They will always round up/down so:

  • RoundUp 99 to the factor of 100 → 100
  • RoundDown 99 to the factor of 100 → 0
6

Thanks guys,

I had a short circuit - wanted it to calc the next largest, rather than nearest…

I’ll clean my glasses.

P

7

And, [could] rounded numbers be impacted by the infamous javascript floating point error as well?

8

Very good article. I’ve had a few problems with floating point errors in Coda.
I’m going to use this trick below from now on.
Instead of:

1
1773×176 13.1 KB

this:
2
2788×185 15.4 KB

9

This isn’t specific to coda, it’s a consequence of the binary floating-point system, it’s seen in every programming language. Here’s a relevant SO thread