Re: Time format data as a string?

[Daniel J S. <dan...@ie...>]

On 11/21/2016 12:12 PM, Ethan A Merritt wrote:
> 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

I did try this the other day when I was busy working on some code.  It 
does work, thanks.  I think this would be a good example to include as 
well, simply because it seems a more natural way to think of things for 
computer users, i.e., the two columns and also that a date/time field 
would be thought of as a string.

Dan