Smooth edge on contour plot

Hello,

In my contourf plot, I want to cut off values above a certain limit, 61 in this case. In the attached figure, I want to have the figure on the right to look like the figure on the left upto the 61 line. However if I set these values to either zero or nan, the edge will always be tapered. Is there a way display the edge like a smooth contour line, like all others in the figure?

Thanks in advance!

The figure on the left is created by

figure()
contourf(W_chh*10^6,W_ww*10^6,(Twout'))
colorbar

The figure on the right is created by

figure()
Twout(Twout >= 61) = nan;
contourf(W_chh*10^6,W_ww*10^6,(Twout'))
colorbar

[ADSW121365]

You might be able to force the behaviour by plotting the full graph, then setting an xlim to crop out the extra part of the graph without deforming your curves.

[Lars Peters]

Thank you for your answer, however if I limit the colorbar in the original figure, all values above 61 will get the color coresponding to the maximum value set as limit, and will still be in the graph. In this case, these values are physically not possible and therefore need to be removed completely.

[Adam Danz]

If you want the colors to have the same definition for both plots, you can set the color limits of the second axes to have a range from ~56 to 64 or whatever the range is in the first plot. Currently, "yellow-ish" means ~63 on the plot on the left but the same exact color means ~60 on the plot on the right.

[Lars Peters]

It is not about the colors, I will not use the first figure but I just added it as an example. It's about how to get cut off the graph in such a way that there will be a smooth line at the edge, just like this line is present in the first figure at 61 instead of the block line thing that is currently present in the right figure at 61.

[Adam Danz]

It sounds like the step-like contour edge at level 61 is part of your data and you want to modify that controur line as if your data doesn't have that feature in it. I'll update my answer with an alternative.

[Lars Peters]

The same questions holds for this figure, I don't know the values in this case, just the matrix index of the part that needs to be cut off, which I did. Maybe this clears the confusion.

[Adam Danz]

My updated answer suggests to plot the contour lines without modifying the inputs. Then, after the contrours are plotted, remove the levels greater than your threshold.

Answer 1

[Adam Danz]

See the 'levels' option. You could get the levels from the first controur plot and use the same levels for the 2nd plot.

contourf(___,levels)

Also see caxis() to control the color limits so that they match between the two axes.

[update]

Alternatively, you could produce the controur plot without the levels input and then, after plotting, remove levels greater than 61.

[~, c] = contourf(W_chh*10^6,W_ww*10^6,(Twout')); 
c.LevelList(c.LevelList > 61) = []; 

Then add white to the very end of your color map and set the color range so the max values are white.

ax = gca(); 
ax.Colormap(end,:) = 1;  % Max color is now white

A potentially ugly approach would be to get the coordinates of the jagged controur line, smooth them, then replot the smoothed line.

[Lars Peters]

Hello, I have tried that by adding the following, but the edge is still tapered. If I remove the second line, the edge is smooth but then all values larger than 61 will map this value, where I would like them removed.

figure()
Twout(Twout >= 61+273) = nan;
contourf(W_chh*10^6,W_ww*10^6,(Twout'-273),[56:61])
colorbar
caxis([56 61])

[Adam Danz]

You could alter your colormap so that values >61 are mapped to white.

[Lars Peters]

Thank You!

[Adam Danz]

Glad I could help.