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Any way to extract data from contour plots using paraView?

Hi all,

I have a newbie question about how to extract x, y coordinates of interpolation points on a contour and their interpolated field values by using paraView?

Thanks.

Angela:)

after contour
choose : Filters -> Data analysis -> integrate Variables

then a new window will open, then in "showing" tab , choose "contour"

if you want to save data in ".csv" you can choose : file -> save data

Quote:

Originally Posted by nimasam (Post 280947)

Thanks a lot~ I works cool~~~:)

I have also exported my contour data and the export seems fine. However, I plan to plot the contour with tikz.
It seems that the contour data is highly unsorted. Thus, the tikz plots don't look like they should. Is there any way to pre-sort the contour lines before exporting or do I have to manually piece the points together?

Cheers
Alex

Quote:

Originally Posted by Kina (Post 608089)

I am in a similar situation with gnuplot. The data exported from paraview is unsorted and 'plot with line' option makes zig zag-lines. I tried to sort the data using the contour values but doesn't work as I expected. Did you find any solution Kina? or Somebody know any other way to sort out this?

Thanks

Quote:

Originally Posted by toolpost (Post 673259)

Hey, what's up?

yes, I have managed to sort the contours by coding an octave file that reads in all the unsorted contours and builds a matrix that compares the vector length difference of all points to the current and reconstructs the contours. You might have to do a little tweaking depending on your columns of the .csv output file. This code currently sorts velocity contours I think. You can possibly also run this in matlab although I am not sure if matlab recognizes all the octave syntax correctly.

Proof picture below so you know what it actually looks like afterwards in tikz (or gnuplot, whatever)

Code:

#!/usr/bin/octave -qf

format short



filename = 'yourfile.csv';

M = dlmread(filename,',',1,0); %read in original matrix

% [p U1 U2 U3 N0 N1 N2 x y z]

M = [M(:,6) M(:,7) M(:,8) M(:,5)];        %reduce Matrix to important info

% [x y z u]

M = sortrows(M,2); %sort Matrix Y axis

M = M([(end/2+1):end],:); %isolate positive Y-Values

M(:,2) = []; %delete Y-column

% [x z u]

%M(:,3) = M(:,3) * 1.205; %Calculate real pressure from incompressible

M = sortrows(M,3); %sortieren pressure fields



p = -10^10;

n = 1;

nContours = 1;



% Datei öffnen

ISOPlot = fopen('pressureIsoLines.txt', 'w');

fprintf(ISOPlot, ' x y p \n');



do

        if (M(n,3) != p)

                nContours++;

                n0 = n;

                p = M(n,3);



                do

                        n++;



                        if (n == rows(M))

                                break;

                        endif



                until (M(n+1,3) != p)

                n1 = n;



                MTemp = M([n0:n1],:);        %Temporäre Matrix Pressure-Isoline

                MTemp = sortrows(MTemp,1); %approx. average of matrix

                MTempInit = MTemp;

                MTIso = [];

                MdTemp = [];



                rRef = MTemp(ceil(end/2),:); %start ref point

                MTemp(ceil(end/2),:) = [];        %delete ref



                MdTemp = [sqrt((MTemp(:,1)-rRef(1)).^2 + (MTemp(:,2) - rRef(2)).^2) MTemp];

                MdTemp = sortrows(MdTemp,1); %Matrix: vector differences from ref point



                MTIso = [0 rRef];

                MTIso = [MdTemp(1,:) ; MTIso];



                rRef = MdTemp(1,(2:end));        %new ref point



                for i = 1:rows(MTemp)

                        if (MTemp(i,:) == rRef)

                                MTemp(i,:) = [];

                                break;

                        endif

                endfor



escape = 0;



        do



                rRef1 = MTIso(1,(2:end));        %new ref point

                rRef2 = MTIso(end,(2:end));



                MTempRef = MTemp;

                for i = 1:rows(MTempRef)

                        if (MTempRef(i,:) == rRef1)

                                MTempRef(i,:) = [];

                                break;

                        endif

                endfor

                for i = 1:rows(MTempRef)

                        if (MTempRef(i,:) == rRef2)

                                MTempRef(i,:) = [];

                                break;

                        endif

                endfor



                MdTemp1 = [sqrt((MTempRef(:,1)-rRef1(1)).^2 + (MTempRef(:,2) - rRef1(2)).^2) MTempRef];

                MdTemp1 = sortrows(MdTemp1,1); %new vector diff matrix

                if (rows(MdTemp1)>0)

                        dCheck1 = MdTemp1(1,1);

                else

                        dCheck1 = 10e3;

                endif



                MdTemp2 = [sqrt((MTempRef(:,1)-rRef2(1)).^2 + (MTempRef(:,2) - rRef2(2)).^2) MTempRef];

                MdTemp2 = sortrows(MdTemp2,1); %new vector diff matrix

                if (rows(MdTemp2)>0)

                        dCheck2 = MdTemp2(1,1);

                else

                        dCheck2 = 10e3;

                endif



                if (dCheck1 < dCheck2)

                        if (rows(MdTemp1) > 0)

                        MTIso = [MdTemp1(1,:) ; MTIso];

                        rRef = rRef1;        %new ref point

                        endif

                else

                        if (rows(MdTemp1) > 0)

                        MTIso = [MTIso ; MdTemp2(1,:)];

                        rRef = rRef2;        %new ref point

                        endif

                endif



        if (rows(MTemp) > 2)        %delete ref point

                for i = 1:rows(MTemp)

                        if (MTemp(i,:) == rRef)

                                MTemp(i,:) = [];

                                break;

                        endif

                endfor



        else

                MTemp = [];

                escape = 1;



        endif



        until (escape == 1)



        endif



        if (n < rows(M))

                n++;

        endif



        for i = (1:rows(MTIso))



                fprintf(ISOPlot, ' %f %f %f \n', MTIso(i,2:end)');



                if (MTIso(i,1) >= 0.15)

                        fprintf(ISOPlot, '\n');

                endif



        endfor



fprintf(ISOPlot, '\n');



until (n == rows(M))



fclose(ISOPlot);

Quote:

Originally Posted by Kina (Post 673282)

Hello Kina!

Thanks for the code! I have been searching yesterday and trying to tackle with a matlab code 'points2contour', which I found in mathworks website. I will try to modify your code as per my data and let you know the results. Also, I use octave, not comfortable with matlab. :)

Your reply and willingness to help is really appreciated.

Thanks

Quote:

Originally Posted by toolpost (Post 673376)

Yeah alright! Just to tell you one or two lines for better understanding: the code takes the first point of each contour it reads from the file and tries to find the nearest point of the same contour by the minimal distance. Then, the point is removed from the original file matrix. If the distance exceeds a certain threshold, it switches over to the next contour. That's what I remember from it. If you use octave you should be able to follow the code. It worked for me.

Cheers

Quote:

Originally Posted by Kina (Post 673449)

Hi Kina!

Thanks for the detailed info. I have used the code without much modifications, though I faced some minor issues. I noticed that an iso-contour from paraview bears not exactly same contour values, minor deviations in the order of 0.001 were present. So, I had to re-export the data from paraview with precision set to 4, and thus able to sort most of the contours. Still,some repetitions and random jumps were there. But, I managed to edit the output file manually without much headache. Please see the figure attached.

Thanks again for the help!

Jabir

Quote:

Originally Posted by toolpost (Post 673724)

Hey Jabir,

looks good so far :) some minor manipulation of the output was also necessary for me. Instead of lowering the output resolution you could have also put in another threshold for the p value in form of changing:

Code:

do

        if (M(n,3) != p)

                nContours++;

                n0 = n;

                p = M(n,3);

at the beginning to

Code:

do

        if (M(n,3) < 0.99 * p || M(n,3) > 1.01 * p)

                nContours++;

                n0 = n;

                p = M(n,3);

which would give you roughly 1% of tolerance of the referenced p value before switching over to a new contour. Apart from that: glad I could help you!

Best wishes for the rest of your project
Alex

Quote:

Originally Posted by Kina (Post 673742)

Code:

do

    if (M(n,3) != p)

        nContours++;

        n0 = n;

        p = M(n,3);

at the beginning to

Code:

do

    if (M(n,3) < 0.99 * p || M(n,3) > 1.01 * p)

        nContours++;

        n0 = n;

        p = M(n,3);

which would give you roughly 1% of tolerance of the referenced p value before switching over to a new contour.

Hello Alex!

That's a cool idea to give some tolerance to the contour magnitude. I will definitely try this next time.

Thanks for your help. I really appreciate it. :)

Jabir