Re: [Gnuplot-info] Problem with date format

[Thomas S. <t.s...@fz...>]

...it's not so easy to repair...

what happens:

in 'axis.c':

'setup_tics' is called. and because 'timelevel[axis]' is not set
'quantize_time_tics' is used to set 'timelevel[axis]' as a byproduct.

and if 'quantize_time_tics' decides to set
   timelevel[axis] = TIMELEVEL_MONTHS
because the axis range is too large (more than 20 weeks in the example
below), then the tics increment may still be 1 week (604800s) and the
loop to produce the tics is iterating correctly in 'gen_tics',
BUT 'time_tic_just' is called for each tic, adjusting the tic to a grid
based
on 'timelevel[axis]' which in this case is 'TIMELEVEL_MONTHS', i.e. all
four tics per month fall on the 1st day of the month.

to repair this 'timelevel[axis]' should be set according to the tics
increment
specified by the user, so something like in the subroutine 'setup_tics' in
'axis.c' could work:

   if (this->is_timedata && ticdef->type == TIC_SERIES)
-      quantize_time_tics(axis, tic, fabs(this->max - this->min), 20);
+   {
+      if (tic >= 365*24*60*60.) timelevel[axis] = TIMELEVEL_YEARS;
+      else if (tic >= 28*24*60*60.) timelevel[axis] = TIMELEVEL_MONTHS;
+      else if (tic >= 7*24*60*60.) timelevel[axis] = TIMELEVEL_WEEKS;
+      else if (tic >= 24*60*60.) timelevel[axis] = TIMELEVEL_DAYS;
+      else if (tic >= 60*60.) timelevel[axis] = TIMELEVEL_HOURS;
+      else if (tic >= 60.) timelevel[axis] = TIMELEVEL_MINUTES;
+      else timelevel[axis] = TIMELEVEL_SECONDS;
+   }


Thomas Sefzick wrote:
> 
> if your xrange is 20 weeks or lower , e.g.
> 
>     set xrange ["01/01/2007":"20/05/2007"]
> 
> everything works as expected, but if you exceed 20 weeks,
> 
>     set xrange ["01/01/2007":"21/05/2007"]
> 
> xtics are placed at 'beginning of month' and mxtics are drawn
> at wrong positions.
> 
> this behaviour has nothing to do with the actual number of tics
> on the x-axis.
> 
> it seems to be some mechanism in 'axis.c' which should prevent
> the axis from getting overcrowded with tics.
> (see 'quantize_time_tics' in 'axis.c' which is calling
> 'quantize_duodecimal_tics' or - as in your case -
> 'quantize_normal_tics')
> 
> don't know how to solve this :-(
> 
> thomas
> 
> 
> Cameron Horsburgh wrote:
>> 
>> Hi folks,
>> 
>> I'm using the Debian version of gnuplot 4.2 patchlevel 2.
>> 
>> I have a file (data.dat) with two columns. The first contains 
>> dates and the other contains measured data:
>> 
>> 03/03/2007 89.8	  
>> 04/04/2007 85.4
>> 05/05/2007 79.0
>> 12/06/2007 78.3
>> 18/07/2007 77.0
>> 13/09/2007 65.6
>> 29/12/2007 65.0
>> 
>> I wish to graph my data (y axis) against the date (x axis).
>> I want the x axis to show day of the month and the month, and
>>  increment weekly. So I use the following list of commands:
>> 
>> 
>> 
>> set xdata time
>> set timefmt "%d/%m/%Y"
>> set format x "%d/%m"
>> set xtics "03/03/2007",604800 # number of seconds in a week
>> plot "data.dat" using 1:2 notitle
>> 
>> 
>> 
>> The output isn't what I expect. The major tics all seem to round to
>> the first day of the month and several minor tics appear after each
>> major. If I change a few things around --- for example, change the x
>> format to other units, change the increment size, etc, the same thing
>> happens. All xtics round to the nearest first of the month.
>> 
>> The data itself plots correctly
>> 
>> I've looked through the documentation but I seem to be missing
>> something fairly obvious. Can anyone help?
>> 
>> -- 
>> 
>> =============================================
>> Cameron Horsburgh
>> 
>> =============================================
>> 
>> 
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>> 
> 
> 

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