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

[<pl...@pi...>]

On 04/23/14 20:47, Ethan A Merritt wrote:
>
> 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
>
>

Is it a safe bet that no one has a script that relies on meaningless junk?

This was presumably an oversight when NaN was added. Is anyone really 
using this "feature"?

It's more an inconsistency than a howler of a bug, so wouldn't v5 be a 
good opportunity to profit from the relaxation of b/c rules and fix it?

What is the most consistent with a terminal plot ?  Terminals produce no 
output for NaN points. Producing no output into the table would seem to 
be the best equivalent to me. That is the behaviour I was expecting , at 
least.

There may be a case for outputting NaN in column 1 and the expression in 
col 2 but this could fail , for example , if I was doing the NaN trick 
to prevent evaluation of the expression in a range where it would fail.

f(x)=1/x;
  plot datafile using   (($1<0)?$1:NaN):(2 * f($1))

so perhaps NaN NaN  ??

I think no output is the most consistent with no point in a plot unless 
  someone can see something I've missed.

/Peter