Re: [Plplot-general] Test of plhist problem - it is empty again

[Arjen M. <Arj...@de...>]

Hi Sergey, Alan,

> -----Original Message-----
> From: Alan W. Irwin [mailto:Ala...@gm...]
> Sent: Monday, November 19, 2018 8:23 PM
> To: Arjen Markus
> Cc: Sergej Scherbina; plp...@li...
> Subject: Re: [Plplot-general] Test of plhist problem - it is empty again
>
> On 2018-11-19 07:38-0000 Arjen Markus wrote:
>
> > Hi Sergey,
> >
> > Odd, it is something I will have to check more closely then. I have used the trunk
> by the way, but I am not aware that things have changed much in that part of the
> code.
>
Last night, I had a closer look at what was going on and it turned out that the variables FloatStartDate and FloatStoptDate (there seems to be one "t" too many in there ;)) got values that were outside the range of the data in the input file. I used "2018-10-08 00:00:00.110 2018-10-17 00:00:00.129" as the relevant arguments - as from the example, but it may be that on the Cygwin platform I used the times are converted differently. This explains the error message I got: there were no data on which to base the extremes.

> To Arjen and Sergey:
>
> I have done that close check for the current tip of the master branch (which is going
> to be changed only in a minimal way when the 5.14.0 release is completed).  And
> all is well with our plhist call there, i.e., it produces the expected non-empty
> histogram.
>
> @Sergey:
>
> I suggest you look closely at standard example 5 (the only one that uses plhist).  If
> you build it and also some device, then
>
> examples/c/x05c -dev <some_device>
>
> just works correctly for my Debian Buster platform.  That is, it shows the desired
> histogram, i.e., exactly the same rendered results as can be seen at
> <http://plplot.org/examples.php?demo=05>.
>
> Do you get that same histogram result if you replace your code with that from
> standard example 5?  If so, then the next obvious question is what changes you
> have made from that good plhist call in standard example 5 to the call in your own
> code that is causing an empty histogram for you.
>
When I had corrected the immediate problem by setting the two variables to more reasonable values, I got a nice xy-plot and an empty histogram. Then I looked at the implementation of plhist() - and realised that it is meant to plot a distribution of the data. The data that are passed should match the x-axis, in this case the times, and the minimum and maximum on which to base the bins should match the x-axis as well. However, the code as I have been using it from the tarfile, passes the y-values (FloatData) and the minimum and maximum times.

So I changed the argument to FloatDate instead. The plot is still empty though, the 22 data points do not show up in any way. At least this gives us a starting point to analyse the problem.

Regards,

Arjen
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