Could you please tell me the difference between "Fill to Contour Lines" and "Fill to Grid Lines"? Or what does "grid line" mean exactly here? If I select "Fill to Contour Lines", looks like some sort of smoothing is applied (see Fig. b) compared to "Fill to Grid lines" (see Fig. a). What I need is a contour plot without any smoothing. Thank you!
Grid lines are the actual data cells. Each cell is displayed in the color specified by the contour color map, so it looks like you have about 30 columns and twice that many rows in your matrix. If you go to your matrix - I assume you have a matrix since the fill options are different for a virtual matrix - and press Ctrl+Shift+I you will see the image view (albeit in black and white) which should look like a flipped version of your graph. Flipped, because matrices increase Y going down while contour plots display Y going up.
Fill to Contour Lines is indeed a kind of smoothing since it finds the best path through for data for each contour Level.