Fix the trace in the plot

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sally_wu
sally_wu on 6 Feb 2016
Commented: Star Strider on 7 Feb 2016
Is there a way somehow to get rid off the cross-line in this traces? For some reason,I am getting this cross-line that I do not want to! Any suggestions? Thanks
  1 Comment
Stephen23
Stephen23 on 6 Feb 2016
Edited: Stephen23 on 6 Feb 2016
We need to see your data. Please upload it: click the paperclip button, then both the Choose file and Attach file buttons.

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Answers (3)

Star Strider
Star Strider on 6 Feb 2016
Without your data, it’s difficult to say. One way would be to delete the last element of each of your x and y vectors:
x = [1:10 1];
y = randi(9, 1, 10);
y = [y y(1)];
figure(1)
subplot(2,1,1)
plot(x, y) % Original Data
subplot(2,1,2)
plot(x(1:end-1), y(1:end-1)) % Delete Wrap-Around
Run this little code snippet to see the cause and effect of the change.
  4 Comments
sally_wu
sally_wu on 6 Feb 2016
Edited: sally_wu on 6 Feb 2016
ref=81;
slice=500;
A1 = loaddata('a2.txt');
d =size(A1);
j=0;
for i=1:d(1,1);
if(A1(i,1)==slice);
j=j+1;
a(j,1)=A1(i,2);
b(j,1)=A1(i,4)-ref;
end
plot(a(1:end-1), b(1:end-1))
grid on
end
My apologies, but it did not work out...I am still getting that annoying cross-line, which I do not want to..
Star Strider
Star Strider on 7 Feb 2016
Please upload your data, preferably as a .mat file. Without having it to work with, I can only guess as to what the problem is (and thus far, that doesn’t seem to be productive for either of us).
Use the ‘paperclip’ icon to upload it, and then complete both the ‘Choose file’ and ‘Attach file’ steps.

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Azzi Abdelmalek
Azzi Abdelmalek on 6 Feb 2016
Get ride of the last point in your plot

Geoff Hayes
Geoff Hayes on 6 Feb 2016
sally - I suspect that if you are plotting something similar to
plot(x,y)
then some of your x values are out of order (i.e. 5000,5001,6799,6800,5002,5003,etc). For example, if I want to plot the curve
y = x^2;
where x is defined as
x = linspace(-25,25,1000);
which I then re-arrange (or sort out of order) the x values as
x = [x(251:end) x(1:250)];
I will observe the following upon plotting
y = x.^2;
plot(x,y)
I get the same "cross-line" as you! To correct, you can try to sort the x and y values as
data = sortrows([x' y']); % sort on first column
x = data(:,1);
y = data(:,2);
plot(x,y);
which should plot as expected without the undesirable line.

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