Contourf is plotting weird lines. How to remove them?

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MDias
MDias 2020-5-22
评论： MDias 2020-5-23
Hi,
I'm using hist3 to get bin centers and the elements in each bin. After this I use contourf to plot the data. Unfortunatelly the outputed contour figure has small vertical and horizointal black lines that don't seem to make sense. Please see lines inside red circles for examples:
My code is as follows:
edges = {0:0.2:13 0:0.2:13}; % edges for hist3
insetPos = [.52 .53 .35 .35];
[n,c] = hist3(X,'edges',edges);
figure
heatmap(n) % FEX
% contourmap
axes('Position',insetPos)
box on
contourf(c{1},c{2},n)
I belive the black lines are part of the contour lines, yet they appear where there are no boundries. If I remove the contour lines they also go away.
contourf(c{1},c{2},n,'LineColor','none') % no contour lines
Any tip on how I could keep the contour lines without drawing the "intruding" lines?

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采纳的回答

Kelly Kearney
Kelly Kearney 2020-5-22
When you let contour choose contour levels automatically, it doesn't always choose the levels you really want. In this case, it chooses integer values, which may not be the best way to contour all-integer data. You might have better luck getting the look you want if you specify between-integer levels, e.g.
contourf(c{1}, c{2}, n, -0.5:10.5)
  1 个评论
MDias
MDias 2020-5-23
Thanks Kelly!
Like Walter pointed out I didn't carefully at n...or at contourf for that matter. This does what I need.

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更多回答（2 个）

KSSV
KSSV 2020-5-22
Use pcolor with shading interp instead of contourf.
  3 个评论
显示 1更早的评论
KSSV
KSSV 2020-5-22
On this use holdon and plot contour lines using countour.
MDias
MDias 2020-5-22
The unwanted bits of the contour (small black lines highlighted above) are still there.

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Walter Roberson
Walter Roberson 2020-5-22
Look at n(24,9) and see that it is 1 there, corresponding to x=1.7, y=4.7; n(23,9) is also 1. That is an island of two 1's surrounded by 0's. With the contour levels happening to correspond to the integers, there should be an island there.
spy(n) and you will see there are a number of small islands.
  2 个评论
Walter Roberson
Walter Roberson 2020-5-23
if you take
n.*bwareafilt(n>0,[SIZE, inf])
then it would filter out islands smaller than SIZE pixels
MDias
MDias 2020-5-23
Thanks Walter!
Now this makes sense, I did not look carefully at n...

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