Make Line chart not show (Contain Formula)

Hi all,
I have a little too big problem when drawing Line chart, some of the cell that contain formula but in chart it shows 0 value, I don't want to draw the line to zero as I put in formula to make that cell blank but it still show zero???

Can you help me on this, thank you very much!

I search for it and turn out I need NA() instead of blank ("")
Tkss