Re: what is the use of "u" in tabulated output?

[Ethan A M. <sf...@us...>]

On Sunday, 20 April, 2014 10:48:10 pl...@pi... wrote:
>   HI,
> 
> 
> I often use conditional using clauses to plot part of a range of data
> 
> plot datafile using   (($1<=1995.55)?$1:NaN):(2*fcos1($1))
> 
> I tried this when writing to a file specified with "set table"  and 
> instead of cutting off the output, it appends garbage data with a "u".
> 
> help table tells me this means "undefined"
> 
> I see two problems here. I did not ask for undefined output , I 
> specified NaN.
> 
> Secondly , what is the possible use of "undefined" values in a data file?
> 
> 1995.46  1.00914  i
> 1995.54  1.10947  i
> 1.98547e-81  4.74363e+170  u
> 3.75845e+174  7.52884e-24  u
> 0  2.122e-314  u
> 0  0  u
> 0  0  u
> 1.9771e+161  1.44402e+214  u
> -1.22337e-44  1.1735e-319  u
> 1.01887e+189  7.49746e+247  u
> 5.35166e+199  2.10124e+88  u

I do not know what the original idea was,
nor do I know if there are existing scripts that depend on the 'u'.
It does seem pointless to write out total junk values as in your example.

If it helps, version 5 has a new mode "with table" that does what you want.

gnuplot> set samples 11
gnuplot> set xrange [0:10]
gnuplot> set table
gnuplot> plot '+' using ((4<$1&&$1<8) ? NaN : $1) : ($1**2) with table
 0 0
 1 1
 2 4
 3 9
 4 16
 nan 25
 nan 36
 nan 49
 8 64
 9 81
 10 100
gnuplot> 

This is not ideal because it requires a separate plot style, which means
you can't do
    plot $foo;   set table;   replot

Should tabular output of the regular plot styles be changes to match this?
What, if anything, depends on the old behavior and would break?

	Ethan