Re: Time format data as a string?

[Ethan A M. <sf...@us...>]

On Friday, 18 November, 2016 22:06:54 Daniel J Sebald wrote:
> I just used the time format in a plot.  It's nice, incorporating the 
> date and time and all.  So thank you to whomever.
> 
> It did take me a bit to figure out though why something like this failed:
> 
>    set timefmt "%m/%d/%y %H:%M"
>    plot "data" using 1:2
> 
> with data something like
> 
> 03/03/16 11:30	23.5
> 03/03/16 11:45	24.8
> ...
> 
> It's because the datafile.c reading routine recognizes that first space 
> as a delimiter such that field ':2' is actually 11 in both cases shown. 
>   That's fine, as the following works:
> 
>    plot "data" using 1:3
> 
> and the documentation gives proper examples and all, if not explicitly 
> stating.
> 
> However, it's a bit of a mental juxtaposition because the person 
> scripting the code is thinking of the "03/03/16 11:30" as the "first" 
> entry.  Now, gnuplot has string inputs, such as in energy_circles.dat of 
> the demo subdirectory.  So, I'm wondering if the the date/time data 
> entry could also accept a datafile string.  It shouldn't be too much of 
> a C-code alteration.  For example, this might be the equivalent to the 
> above:
> 
>    plot "data" using 1:2
> 
> with data
> 
> "03/03/16 11:30" 23.5
> "03/03/16 11:45" 24.8
> ...
> 
> I tried that, and gnuplot doesn't allow it

Gnuplot does allow it.
Your test commands and data are plotted correctly so long as you
tell gnuplot that it is wrapped in a string:

   plot "data" using (strcol(1)):2

where strcol(N) is shorthand for stringcolumn(N)

	Ethan