How to: Merging multiple graph lines

Question

Patrick 2014-10-18

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https://ww2.mathworks.cn/matlabcentral/answers/159160-how-to-merging-multiple-graph-lines

编辑： vi trung kien 2018-3-21

Hello Guys,

my problem is that I have several data sets of different x-Arrays and always the same y-Array. Basically my plot functions looks like this: plot(x1,y,'g',x2,y,'b'....)

As I have drawn in the picture I want to merge all the lines as to always keep the lowest y-values going from left to right in terms of x-values. This should creat one single new plot that looks like the black line in the right picture. The left picture demonstrates the overlapping data sets.

Can I solve this problem graphically, e.g. using a plotting function to always display the lowest y-value or do I need to create a new 2D array that always picks the lowest y-value for every x- value? Maybe you can give me a base to start from. Sorry about my "untechnical" explanation, Im new to Matlab and coding in general.

Thanks in advance for your support. Pat

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Guillaume 2014-10-18

It looks like you meant to attach or (better) embed a figure, but seems like you forgot

Patrick 2014-10-20

Thanks Guillaume,

just attached the image.

Regards Pat

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Answer 1

Guillaume 2014-10-20

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https://ww2.mathworks.cn/matlabcentral/answers/159160-how-to-merging-multiple-graph-lines#answer_155850

编辑：Guillaume 2014-10-20

在 MATLAB Online 中打开

I would concatenate all your x, get the unique values and their position and use the position with accumarray to get the minimum of y:

xall = [x1 x2 x3 ...];
[x, ~, indices] = unique(xall);
y = accumarray(indices, repmat(y, 1, N)', [], @min); %where N is the number of xi
plot(x, y);

edited for missing comma

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Patrick 2014-10-23

在 MATLAB Online 中打开

Unfortunately, they do not match. Here is my code if that helps:

      kcb = 1345,618472;  
for i=1:length(f);               % Sortiere alle Einträge der Frequenz
    if ReG(i)<0;                 % und des Realteils nach Realteil < 0
        ReG(i) = ReG(i);         % und erstelle neue Vektoren für Realteil
    else ReG(i) = 0;             % und Frequenz
    end;
end;
n1 = 60.*f./(1-1./pi.*atan(ReG./ImG));
n2 = 60.*f./(2-1./pi.*atan(ReG./ImG));
n3 = 60.*f./(3-1./pi.*atan(ReG./ImG));
n4 = 60.*f./(4-1./pi.*atan(ReG./ImG));
n5 = 60.*f./(5-1./pi.*atan(ReG./ImG));
n6 = 60.*f./(6-1./pi.*atan(ReG./ImG));
n7 = 60.*f./(7-1./pi.*atan(ReG./ImG));
n8 = 60.*f./(8-1./pi.*atan(ReG./ImG));
n9 = 60.*f./(9-1./pi.*atan(ReG./ImG));
n10 = 60.*f./(10-1./pi.*atan(ReG./ImG));
bcr = 1./(2.*kcb.*abs(ReG).*1000)   % Formel der Grenzspanungstiefe und
for j=1:length(f);
    if bcr(j) < 10^10;
        bcr(j) = bcr(j);
    else bcr(j) = 0;
    end;
end;
for k=1:length(f);
    if bcr(k)< 10^(-10);
        n1(k) = 0;
        n2(k) = 0;
        n3(k) = 0;
        n4(k) = 0;
        n5(k) = 0;
        n6(k) = 0;
        n7(k) = 0;
        n8(k) = 0;
        n9(k) = 0;
        n10(k) = 0;
    end;
end;
bcr = nonzeros(bcr);
n1 = nonzeros(n1);
n2 = nonzeros(n2);
n3 = nonzeros(n3);
n4 = nonzeros(n4);
n5 = nonzeros(n5);
n6 = nonzeros(n6);
n7 = nonzeros(n7);
n8 = nonzeros(n8);
n9 = nonzeros(n9);
n10 = nonzeros(n10);
figure(1)
plot(n1,bcr,'b',n2,bcr,'r',n3,bcr,'y',n4,bcr,'m',n5,bcr,'m',n6,bcr,'g',n7,bcr,'k',n8,bcr,'b',n9,bcr,'r',n10,bcr,'y')
title('Stabilitätskarte')
xlabel('Drehzahl n [1/min]')
ylabel('Grenzspanungstiefe bcr [mm]')
figure(2)
nall = [n1; n2; n3; n4; n5; n6; n7; n8; n9; n10];
[n, ~, indices] = unique(nall);
bcr = accumarray(indices, repmat(bcr, 1, 10)', [], @min);
plot(x, y);

Here are the dimensions of the Variables:

f 201 x 1

ReG 201 x 1

bcr 197 x 1

ImG 201 x 1

n1 to n10 197 x 1

nall 1970 x 1

Do you have any other ideas how I can progress with my script?

Thanks a lot for your help so far. I hope we can solve this together Regards Pat

Patrick 2014-10-26

Thanks for your reply, I will see what the results might be, but I get your point with the noise. That's the reason I was looking for a graphical approach to my problem in the first place. Do you know of any other mehtod tol realize what I pointed out in the attached image?

Patrick 2014-10-27

stabilitylobe.png

Okay, I put the resulting diagram into the attachment. For my purpose the occurring noise is not really significant. Thanks a lot for your help, Guillaume!

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Answer 2

Rick Rosson 2014-10-18

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https://ww2.mathworks.cn/matlabcentral/answers/159160-how-to-merging-multiple-graph-lines#answer_155704

在 MATLAB Online 中打开

   x = [ x1 x2 x3 ... ];
   N = length(x)/length(y);
   y = repmat(y,1,N);
   plot(x,y);

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Patrick 2014-10-20

forum.png

Hello Rick,

thanks for your answer! It gives me the same results as my previous code though:

figure(1) plot(n1,bcr,'b',n2,bcr,'r',n3,bcr,'y',n4,bcr,'m',n5,bcr,'m',n6,bcr,'g',n7,bcr,'k',n8,bcr,'b',n9,bcr,'r',n10,bcr,'y')

VS:

figure(2) n = [n1 n2 n3 n4 n5 n6 n7 n8 n9 n10]; N = length(n)/length(bcr); bcr = repmat(bcr,1,N); plot(n,bcr)

However, I dont want 10 individual graph lines in one diagram. What I need is one single united line that always displays Ymin(n), like I have scatched in the pictures attached.

Oops, sorry about that attachment. Forgot to hit the "Attach file" button.

vi trung kien 2018-3-21

编辑：vi trung kien 2018-3-21

Dear Patrick, Can you suggest for me how to get one single united line that always displays Ymin(n), like you have scratched in the pictures attached.My problem the same as you before. Thanks for your help.

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