I have to admit I have some confusion about the whole Cartesian graph thing. The first example is obviously a Cartesian graph and needs no numeric indicator on the axes values. If you could give me a day, I will check with someone who is more knowledgeable about math things, just to be sure.
I discussed this with a member of the Tactile Graphics committee. TG guidelines cover the use or non-use of the numeric indicator in graphs. The consensus: if you can tell from context that it is a coordinate plane, but only quadrant I, the number signs should be left off. If it appears to be a line graph or bar graph, number signs are needed. Since this one is named as a coordinate plane, the numeric indicator is not required.