Discussion: What to do if NaN appears in a non-coordinate field?

[sfeam (E. Merritt) <eam...@gm...>]

Bug #3513138 reports a problem when NaN appears in a data column 
where gnuplot is expecting to find an extra property.  
The example given is
     plot 'foo' using 1:2:3 with points lc palette
The same problem would happen for
     plot 'foo' using 1:2:3 with points pointsize variable

If NaN appears in the x, y, or z coordinate then the point
is rejected on input.  But what should we do for these 
cases where the point is in range on x/y/z but a separate
field is missing or NaN?

1) Ignore the point (same as a NaN coordinate).

2) Accept the point but assign the property some default value.

3) Use the coordinates for auto-scaling but do not draw it.

4) Something else

The current handling of "with image" data provides some precedent.
A NaN image pixel is either not drawn at all or is rendered
in the background color. But the issue of auto-scaling does not 
arise for image plots because omitting a single pixel would not 
change the range.

Should an "invisible" point (i.e. one with NaN for pointsize or
color) contribute to auto-scaling?

There are probably more obscure cases also, like "with circles" 
where the radius is NaN.  Can you think of any others?


	Ethan