Why is the contour different when a) manually taking the log10 of the data vs b) using options like 'XScale','log'?

Hi there,

I am plotting contours in MATLAB and noticed that the contours look different when I:

• Manually take the logarithm of both x and y data

figure
contour(log10(x),log10(y),INR1,[1,1],'Color','r','LineWidth',1.2)
hold on
contour(log10(x),log10(y),INR2,[3.6,3.6],'Color','b','LineWidth',1.2)

• Use the XScale and YScale options

figure
contour(x,y,INR1,[1,1],'Color','r','LineWidth',1.2)
hold on
contour(x,y,INR2,[3.6,3.6],'Color','b','LineWidth',1.2)
set(gca,'FontSize',18,'XScale','log','YScale','log')

I am not too sure what have I done wrong here. Please let me know if you have any ideas. Thank you in advance!

[Jan]

Please post the data. It looks so strange!