Re: [Gnuplot-info] plotting time series data

[Roderick S. <rod...@gm...>]

thanks to all for your help.

Ethan’s suggestion works great.

Rod

--
Roderick Stewart
Research Fellow (Volcano-Seismology), Montserrat Volcano Observatory
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> On 15 Mar 2021, at 18:10, Ethan Merritt <eam...@gm...> wrote:
> 
> On Monday, 15 March 2021 13:20:14 PDT Roderick Stewart wrote:
>> I’m new to gnuplot (love it!) but can’t work out how to plot time series data from a file when the file contains no time information, just equally-spaced data values.
>> 
>> I have a binary file which has one year’s worth of data at 1-minute intervals.
>> 
>> I can plot it using:
>> 
>> plot ‘2021.dat’ binary format=“%int32” using 0:1
>> 
>> But I want the X axis to be a date axis so I can, for example, set xrange.
>> 
>> How do I get the timestamps into the plot?
> 
> The units of time in gnuplot are seconds.  
> A date corresponds to the number of seconds elapsed since the start of the
> epoch (1 Jan 1970).
> 
> Each record in your data adds 60 seconds to the date.
> So the task is
> 1) Determine the canonical date (number of seconds since 1970) of the start time.
> 2) Add 60 seconds for each data point
> 
> Suppose your data starts with the first minute of 2021.
> 
>  timefmt = "%d-%b-%Y"
>  time0 = strptime( timefmt, "01-Jan-2021" )
> 
>  # the xrange and tic placement will use the timefmt we just set
>  set xdata time
>  set xrange [time0 : *]
>  set xtics ("01-Jan-2021", "01-Feb-2021", "01-Mar-2021")
> 
>  # the actual tic labels will only use the month name 
>  set xtics format "%b"      # Only the month names
> 
>  plot '2021.dat' binary format=%int32" using (time0 + $0 * 60.) : 1 with lines
> 
> 
> 	Ethan
> 
> 
>> 
>> Thanks in advance.
>> Roderick Stewart
> 
> 
>