Why is the "contourf" command plotting my data backwards?

I have data that I would like to plot using MATLAB's "contourf" command.  However, when the data is plotted, it is reflected over the y-axis.  When I use the "contour" command, it plots normally.  Why does "contourf" plot my data backwards?

Answer 1

[MathWorks Support Team]

This behavior is a bug that has persisted until R2014a.  With the introduction of the HG2 graphics system in R2014b, this issue has since been resolved.  Attached is a MAT file with variables that reproduce this issue.  The following example uses these variables to generate both incorrect and correct plots from the same code

>> hold on

>> contourf(xksi_mesh,yksi_mesh,strfun);

>> plot(xksi_mesh ,yksi_mesh ,'b');

Incorrect contour plot (R2014a):

Correct contour plot (R2014b):

The workaround to this issue is to use the "fliplr" command to flip all the data from right to left.  Doing so yields the correct plot in R2014a and below:

>> hold on

>> contourf(fliplr(xksi_mesh),fliplr(yksi_mesh),fliplr(strfun));

>> plot(xksi_mesh ,yksi_mesh ,'b');