Draw arc in scatter graph from arc radius & arc length

Charmwah

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Joined
Jan 23, 2017
Messages
64
Afternoon all...

...I'm trying to use the scatter graph to draw out the extent of an arc, for which I know the radius and the length of the arc itself. These are the only two 'knowns' I have, but from these I can of course work backwards to understand the length of the arc in degrees etc. What I'm struggling with is a way to populate a table of Cartesian X,Y coordinates from which I can then plot the arc perfectly in the graph without it sloughing off as below (it should form a perfect arc, not :

1618572278007.png


Any and all help gladly recieved!
 

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Habtest

Board Regular
Joined
Jul 30, 2020
Messages
197
Office Version
  1. 365
Platform
  1. Windows
With the condition the arc starts on Y axis and go clockwise no more than 90 degree. You may want to define an interval degree of 5-15, sort the coordinates, and finally adjust the axis range and size. The rest is math.

Cell Formulas
RangeFormula
C2C2=PI()/1.5
C6:C25C6=SQRT($C$1^2-B6^2)
B7:B25B7=MIN($C$1*SIN(ROWS(B$6:B6)*$C$3*PI()/180),SIN($C$2/$C$1)*$C$1)


1618576793014.png
 

Charmwah

Board Regular
Joined
Jan 23, 2017
Messages
64
Thanks Habtest, but that doesn't work with my variables of an arc radius of 5.7m & an arc length of 1.19m (or 12°)...

1618577884998.png

With the condition the arc starts on Y axis and go clockwise no more than 90 degree. You may want to define an interval degree of 5-15, sort the coordinates, and finally adjust the axis range and size. The rest is math.

Cell Formulas
RangeFormula
C2C2=PI()/1.5
C6:C25C6=SQRT($C$1^2-B6^2)
B7:B25B7=MIN($C$1*SIN(ROWS(B$6:B6)*$C$3*PI()/180),SIN($C$2/$C$1)*$C$1)


View attachment 36843
 

Charmwah

Board Regular
Joined
Jan 23, 2017
Messages
64
Its the axis sizes that are the problem here isn't it? Thats whats skewing the arc. So how do I set those to ensure the arc is always perfect, as it should be from the maths?
 

Habtest

Board Regular
Joined
Jul 30, 2020
Messages
197
Office Version
  1. 365
Platform
  1. Windows

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Thanks Habtest, but that doesn't work with my variables of an arc radius of 5.7m & an arc length of 1.19m (or 12°)...

View attachment 36844
Yes. Could be slightly different depending on your excel version (would be good to update that part in your account profile), try right each axis figure area, and edit axis bound accordingly as below (both 0~Radius or a little more).

1618719516775.png

Yes
 

Charmwah

Board Regular
Joined
Jan 23, 2017
Messages
64
But is there a way to do this automatically? From a bit of Googling it looks like its a case of manual resizing the axis each time, since both X & Y need different values in order to make the grid 'square' as opposed to skewed to rectangular as is the default...
Yes. Could be slightly different depending on your excel version (would be good to update that part in your account profile), try right each axis figure area, and edit axis bound accordingly as below (both 0~Radius or a little more).

View attachment 36927
Yes
 

Habtest

Board Regular
Joined
Jul 30, 2020
Messages
197
Office Version
  1. 365
Platform
  1. Windows
Maybe automating the sizing via VBA, though not any I know of.
 

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