For loop issue using fprintf to output contour3 levels to file.

Attempting to separate the contour3 output to a file (test.txt) with rows of x,y,z coords to represent contour levels.

My current issue is that I can't see how to make the For loop move to the second level, it stops after outputting the 8 entries of vertices that are in Level A. To be clear, each level is at a particular z-value.

https://www.mathworks.com/help/matlab/ref/contour3.html#mw_e93c9311-7297-49fb-9003-08716e52168e

The link above is the help file for contour3 outputs, it's a bit specific. And those are the formatting rules I'm following.

Answer 1

[Walter Roberson]

I recommend that you use a utility routine from the File Exchange: https://www.mathworks.com/matlabcentral/fileexchange/38863-extract-contour-data-from-contour-matrix-c

[Wthee]

Trying to get an output like the following:

"begin

Point x 1000 y 600 z 10

...

Point x 1050 y 625 z 10

end

...

Point x Xval y Yval z endpoint"

[Walter Roberson]

I never recommend manually decoding the contour matrix. Much better to use a function that has been built already and tested over the years.

Yes, you get back a structure. And then you can easily loop over the structure array elements, easily emitting appropriate prolog and data and epilog for each.

[Wthee]

Thank you

[Adam Danz]

I shared an alternative function on the file exchange that organizes the contour coordinates in a table. The Level column shows the contour level. Since there can be more than 1 contour line at the same level, the Group column is a grouping variable that identifies which contour line each coordinate belongs to.

https://www.mathworks.com/matlabcentral/fileexchange/74010-getcontourlinecoordinates

contourTable =
n×4 table
      Level      Group        X         Y  
    ________    _______    _______    _______
    -5.8504        1        0.44266     -1.75
    -5.8504        1        0.375       -1.8038
    -5.8504        1        0.25        -1.8526
    -5.8504        1        0.125       -1.8498
    etc...