Power duplicate around circle not precise. What am I missing?

[Dangerous]

1 hour ago, GarryP said:

The decimal precision values in “Preferences / User Interface” should only affect the values that the user sees in the UI and should not have any affect on the actual values within the document or how the software works internally.

Can you supply a step-by-step example – a workflow which someone else can follow – showing where this is not true?

If it should only affect what the user sees the why did it only create 213 lines till I altered the precision when it created 214. I really have no interest in seeing the exact angle as long as it uses it which it did not.

All I did was draw an unfilled circle, drew a line from the centre to beyond the circumference, select move tool,  crtl+j to duplicate line around circle centre point, entered angle as 360/214 then ctrl+j till all 214 lines were there.

It is my belief that it rounds up to the set precision as when it has failed 20 times then goes right the 1st time after making precision 6 places it it is not 'just for show' as you claim.

[Dangerous]

1 hour ago, Alfred said:

Did you enter the angle as 360/214 or 1.682243? The former should work correctly, but the latter is slightly imprecise since 360/214 to eight decimal places is 1.69224299.

II entered 360/214. My calculator only gave 6 places although another calculator give 31places.  I could not see any error in the design at 6 digits but set at default of 1 the 214th line went beyond the 360degrees and the 213th was obviously close to the 0 degree line so looked wrong.

[GarryP]

I’ve just tried this:

1. Create circle centred at the centre of the document;
2. Create a horizontal line from the centre of the circle to the right-hand ‘edge’ of the circle;
3. Select the line and Duplicate;
4. In the Transform Panel I selected the left-hand end of the line and pasted 360/214 into the R field;
5. Used Power Duplicate (Ctrl+J) to duplicate the line until it reached where the original line is;
6. My R field now shows a rotation of -0.00032 – see attached image.

To me this shows that there has probably been some rounding going on somewhere but I would expect this as 360/214 produces a very long string of decimal places (31 on the Windows Calculator set to Scientific Mode) and the -0.00032 is still just an approximation for the user.

Plus, being only thirty-two hundred-thousandths of a degree out isn’t too bad for illustration software.

[NotMyFault]

5 hours ago, Dangerous said:

I had a similar issue. I had a circle and wanted 214 radial lines from the centre but Power Duplicate got it wrong. Try as I might it would not work. I realised that the angle of rotation through the duplication process was the issue as 360/214 = 1.682243. With a bit searching I found in PREFERENCES - USER INTERFACE there are settings for decimal places for unit types DEGREE setting changed to 6 and it worked perfectly. There are other settings you can alter the precision for which may help with other issues you may have.

I don't know if that will help in this issue but it did in my situation.

 

Did you use the correct anchor point, or moved the anchor point exactly to the actual center of the circle? 

In my experiments, Power Duplicate is quite accurate, but there are multiple ways to shoot yourself into your own foot when by not caring about all relevant details.

I prefer to move the circle of rotation to an exact pixel position (no fractional digits). In case of a circle centered to the canvas: use non-even canvas size (e.g. 361x361 instead of 360x360), otherwise it will be centered to 179.5 and fractional positions are a prime cause of trouble. You can reduce canvas size latter and move the result after finishing Power Duplicate.