set samples , consistency

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

Hi,

I have fitted an analytic fn to some data using gnuplot and now I want 
to create a synthetic monthly dataset by outputting to "table".

Since gnuplot will always produce a point at start and end of range I 
specify the plot range in integer years and set samples to  (years-1) 
*12 +1 to account for the  last year in the range just having one datum 
point.


plot [1978:2016] cos3(x) * cos2(x)
set samples  (2015-1978)*12+1  # 445
set table "synth.txt"
rep
unset table

This gives the expected number of data lines but the dates are not 
consistent from year to year. There is a small drift in the decimal part 
of the dates.

Only a handful of data lines get an exact beginning of year , ie no 
decimal part:

    awk '($1 !~ /[0-9]\./){print}'  "synth.txt"

# Curve 0 of 1, 445 points
# Curve title: "cos3(x) * cos2(x))"
# x y type
  1978 -0.801801  i
  1981 -0.895154  i
  1994 -0.105538  i
  1997 -0.733846  i
  2000 -0.563258  i
  2013  0.204895  i
  2016 -0.168844  i


On a 200y range it worked as expected. Is there some rounding error 
issue or trick I am missing?

Thanks, Peter.