Re: change in handling missing data.

[Dmitri A. S. <das...@gm...>]

On 8/6/06, Ethan A Merritt <merritt@u.washington.edu> wrote:

> > It is an issue, because previously I did not bother to check
> > if NaNs in my files written as "NaN" or as "nan".
>
> gnuplot reads the number using strtod().
> The linux man page for strtod() says:
>
>       An infinity is either ``INF'' or ``INFINITY'', disregarding case.
>       A  NAN  is  ``NAN''  (disregarding  case) optionally followed by `(', a
>       sequence of characters, followed by ')'.  The character  string  speci-
>       fies in an implementation-dependent way the type of NAN.


Here is the data file ("t3.dat"):
# -- begin
0 2
2 0
NaN NaN
4 2
2 4
# -- end

with gnuplot 4.1 (today's CVS snapshot):
gnuplot> plot "t3.dat"
              ^
         Bad data on line 3

gnuplot> set datafile missing "NaN"
gnuplot> plot "t3.dat"
gnuplot>

(gnuplot 4.0 just plots it)


> That's a bit hard to believe.
>
> How big are your data files?

For the benchamrk I made 2 column data file
x = (-10,10), y = sin(x)
with 1e6 (one million) rows.

cmd is just a one line script
first it is:

plot "t.dat"

[dima@das200 tmp]$ time gnuplot < cmd

real    0m3.814s
user    0m3.488s
sys     0m0.152s

Now changed it to

plot "t.dat" using 1:2

[dima@das200 tmp]$ time gnuplot < cmd

real    0m3.831s
user    0m3.528s
sys     0m0.176s

And finally changed it to

plot "t.dat" using ($1):($2)

[dima@das200 tmp]$ time gnuplot < cmd

real    0m11.086s
user    0m5.828s
sys     0m4.600s

So the wall clock actually increased by factor of 4 mostly due to
"sys" time (originally I just looked at user time -- that is where 150%
came from). I tried both X11 terminal and "dumb" (and output to
/dev/null)  w/o any noticeable difference. These numbers do not
include time of
gnuplot_x11 doing actual drawing.

I did multiple passes, so I am pretty sure the data file is in disk cache.

All this is on FedoraCore 5/ Pentiun4 2.6GHz / 2GB of RAM

>
>         EAM
>

Sincerely,

Dmitri.
--