Polar chart in Excel

[Ralph2]

Hello / Help
Can any one advise me on how to make a decent polar chart in MS Excel...
In a nutshell,
I want to have 12 quantities and location in degrees plotted on a polar chart
Then, draw a circle through those points (a mean average?)
Then, find the center of that circle and compare it to the true center (quantity and location).
All this to do via computer what the API 610 (and others) requires to check the accuracy of a dynamic balance on a rotor. A very convoluted process to do by hand....

Thanks for any advice or direction

 

[LCruiser]

You mean like sines and cosines? Try that concept.

 

[Ralph2]

I can obtain the values but want the display. The API process uses polar graph paper... plot the positions and amplitude... draw a circle to fit all the points... find the center of circle... compare this center to true center... difference is true unbalance...

A very clumsy / crude method but one that is "visually" understandable by customers... I would like to develop a neater and more accurate method yet keeping the visual report

Ralph

 

[IRstuff]

What's wrong with the radar chart type in Excel?

TTFN

 

[electricpete]

Radar chart just plots your points on equally spaced spokes of a wheel. There is no control over the angle other than the angle between spokes is 360 degrees divided by number of datapoints.

I have tried unsuccessfully to use excel to display balance vectors and solution.

As far as the calculation part, there are a series of vector functions that help: Complex converts two arguments (the coordinates in rectangular format) to a complex number; imabs and imargument allow you to display magnitude and angle of complex number; IMSUM and IMSUB for additiona and subtraction; IMPRODUCT if you should need to multiply, and a few more functions beginning with IM.

As far as the diplay part (which was your question), I didn't find any way other than to convert the vectors to rectangular format and then draw the vector by creating a series with two points: the beginning and ending point of the vector. Too much work.

There was an add-in to do this job linked in a previous thread on this exact same subject. I didn't use it because my workplace doesn't allow customizations.

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[electricpete]

This previous thread has link to two prior threads on same subject as well as a link to the add-in for polar plotting:
thread770-132850

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[Ralph2]

Thanks... electricpete
This add-in just may do the trick.. something to start with anyway...

 

[IRstuff]

So what was the issue with conversion from rectangle to polar? Were you using ATAN2 or ATAN? ATAN is not suitable for this sort of thing, since its range is too small. ATAN2 has a range of -pi to +pi

TTFN

 

[Panars]

Check out the polar plot add-in for excel on this website

http://www.andypope.info/charts.htm

 

[vooter]

The polar plot add-in is AWESOME. I used it to make wind roses.