VPP polar diagrams

Discussion in 'Sailboats' started by Eric Sponberg, Dec 16, 2007.

  1. Eric Sponberg
    Joined: Dec 2001
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    Eric Sponberg Senior Member

    Does anyone know if Microsoft Excel can create a polar diagram, such as from VPP output? I have looked into this somewhat in the past and have not come up with an answer, other than it may be possible to create a custom VPP polar diagram in Excel's custom chart function. Has anyone ever done this, and if so, be willing to offer the instructions on how to create one?

    I ask this because I have a fairly good VPP program that runs in DOS, and the output can go to a text file which can then be read into Excel. But the chart does not come through, and the DOS version of the chart does not make a very good presentation. An Excel polar diagram would be much better.

    I welcome anyone's input. Thanks.

    Eric
     
  2. DuncanG
    Joined: Oct 2007
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    DuncanG Junior Member

    The last time I tried this (a few years ago) i couldn't do it in Excel and ended up modifying GnuPlot to get the result I wanted.

    I'll dust it off and see if its still usable.

    You wouldn't happen to have any IMS .off files I could use, would you? What Vpp are you using?
     
  3. tuks
    Joined: Jun 2007
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    tuks Junior Member

    I just tried the standard "radar" chart, it looks ok, but the angle label is oddly placed. I can email the spreadsheet if it would help, it's very rough though.

    Edit : Sorry, just looked a little closer and its not the label placement, the angles are all wrong.
     
  4. gggGuest
    Joined: Feb 2005
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    gggGuest ...

    Yes, but you have to do a lot of fiddling in order to get the angles right.
     
  5. Tim B
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    Tim B Senior Member

    I believe the following GNUPLOT script will do it...

    set polar
    set xrange [0:180]
    set grid
    set xlabel 'True Wind Angle (deg)'
    set ylabel ' Boat Speed (m/s)'
    set title 'Boat Speed at wind speed of #x# m/s'
    plot 'datafile' using 1:2 with linespoints

    That should plot your data. replace 1:2 above, with your x,y columns.

    GNUPLOT manual is at www.gnuplot.info/docs/gnuplot.pdf

    Hope this helps,

    Tim B.
     
  6. Gramp34
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    Gramp34 Junior Member

    You can put individual lines on a plot in Excel by leaving a blank row in the x-y data. Use an X-Y plot with lines but no points, then format the chart until it looks the way you want.

    For example, the data below will draw radial lines from the origin every 30 degrees then a set of arcs. (More points will make the arcs smoother.) Since this is done in an X-Y plot, you need to convert all your polar data to x-y points for plotting.

    You can use additional columns for the y value on each polar line as a different data series, then can format those lines with different colors, etc.

    Hope this helps,

    Tim

    0.00 0.00
    0.00 10.00

    0.00 0.00
    5.00 8.66

    0.00 0.00
    8.66 5.00

    0.00 0.00
    10.00 0.00

    0.00 0.00
    8.66 -5.00

    0.00 0.00
    5.00 -8.66

    0.00 0.00
    0.00 -10.00


    0.00 2.00
    0.68 1.88
    1.29 1.53
    1.73 1.00
    1.97 0.35
    1.97 -0.35
    1.73 -1.00
    1.29 -1.53
    0.68 -1.88
    0.00 -2.00

    0.00 4.00
    1.37 3.76
    2.57 3.06
    3.46 2.00
    3.94 0.69
    3.94 -0.69
    3.46 -2.00
    2.57 -3.06
    1.37 -3.76
    0.00 -4.00

    0.00 6.00
    2.05 5.64
    3.86 4.60
    5.20 3.00
    5.91 1.04
    5.91 -1.04
    5.20 -3.00
    3.86 -4.60
    2.05 -5.64
    0.00 -6.00

    0.00 8.00
    2.74 7.52
    5.14 6.13
    6.93 4.00
    7.88 1.39
    7.88 -1.39
    6.93 -4.00
    5.14 -6.13
    2.74 -7.52
    0.00 -8.00

    0.00 10.00
    3.42 9.40
    6.43 7.66
    8.66 5.00
    9.85 1.74
    9.85 -1.74
    8.66 -5.00
    6.43 -7.66
    3.42 -9.40
    0.00 -10.00
     
  7. MalSmith
    Joined: May 2004
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    MalSmith Boat designing looney

    I have successfully used the Excel radar chart type in the past. I had to use even divisions for the angles to be plotted, even if there there was no data for any individual angle.

    Mal.
     
  8. Pelle
    Joined: Oct 2005
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    Pelle Naval Architect

    There are a number of free scripts for doing polar plots in excel out on the net. Just google "excel polar plot" and you will find plenty to choose from.
     
  9. DuncanG
    Joined: Oct 2007
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    DuncanG Junior Member

    Here's an example from my modified Gnuplot -
     

    Attached Files:

  10. kenJ
    Joined: Jul 2005
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    kenJ Senior Member

    PCSail presents the data in a line graph rather than the polar chart. This is the data from a Pearson 36-2 I recently did. For simplicity I limit the number of vertical wind direction lines, more can be added if desired.
     

    Attached Files:

  11. Tim B
    Joined: Jan 2003
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    Tim B Senior Member

    Sorry,

    The GNUplot script I posted above should have included the following lines, before "plot ..."

    set angle degrees
    set grid polar

    There, that should do it...

    Tim B.
     
  12. Eric Sponberg
    Joined: Dec 2001
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    Eric Sponberg Senior Member

    Gramp34, Thanks for the advice. I created the polar chart from your data, and I can see that that will work quite nicely.

    Tim B, Thanks too. I checked the Gnuplot website, and that looks like some nice Freeware. They seem to have a number of different versions for running on a variety of platforms. I presume I would need to download only one file, but which is the best one for running on Windows XP? They did not make it obvious which one to select.

    Eric
     
  13. Tim B
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    Tim B Senior Member

  14. Emece
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    Emece New Member

    Gnuplot script

    DuncanG,

    Can you post you Gnuplot script?
    Thanks a lot in advance

    Emece
     

  15. DuncanG
    Joined: Oct 2007
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    DuncanG Junior Member

    email sent
     
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