Re: [Gnuplot-info] trendline

[Natu <inc...@rj...>]

On 03/10/2014 05:05 AM, Hans-Bernhard Bröker wrote:
> On 10.03.2014 01:03, Natu wrote:
>
>>      set multiplot
>>      plot "GKLOG001_25452.AVG" using 1:7 with linespoints title "\n5
>> minute min/avg/max" lt rgb "blue";
>>      plot "GKLOG001_25452.MIN" using 1:7 with linespoints title "" lt
>> rgb
>> "green";
>>      plot "GKLOG001_25452.MAX" using 1:7 with linespoints title "" lt
>> rgb
>> "red";
>
> This use of 'multiplot' is ill-advised.  It will not have any positive
> effect compared to a more straight-forward
>
>       plot "GKLOG001_25452.AVG" u 1:7 w lp t "avg" lt rgb "blue", \
>          "GKLOG001_25452.MIN" u 1:7 w lp t"min" lt rgb "green", \
>         "GKLOG001_25452.MAX" u 1:7 wlp t "max" lt rgb "red"
>
>> When I plot certain data files, gnuplot draws a line across the graph
>> showing the increasing/decreasing trend of the data.
>
> I'm reasonably sure this has nothing to do with any trend.  But it's
> hard to know what else it might be, because you don't show any data
> that triggered it.
>

Thank you for all the replies.  Most seemed to think that it was related
to the multiplot.  I have created a very simple example with no
multiplot.  Here are the commands and data that produced this.  I am
running gnuplot 4.4 patchlevel 3 under ubuntu 12.04.  Same problem under
gnuplot 4.2.  I was a little unsure about parsing the date/time from two
columns, but I got that from several web page examples.  It seems to
work correctly.

    set datafile separator ","
    set xdata time
    set timefmt "%m/%d/%y,%H:%M:%S"
    set format x "%H:%M\n%m/%d"
    plot "test4.dat" using 1:3 with linespoints;

Here's the data in test4.dat

03/09/14,23:59:31,61.9
03/09/14,00:09:31,66.5
03/09/14,00:19:31,65.1
03/09/14,00:29:31,66.4
03/09/14,00:39:31,67.6
03/09/14,00:49:31,63.1
03/09/14,00:59:31,62.4
03/09/14,01:09:31,61.3
03/09/14,01:19:31,61.2
03/09/14,01:29:31,68.8
03/09/14,01:39:31,59.8
03/09/14,01:49:31,65.5
03/09/14,01:59:31,61.5
03/09/14,02:09:31,67.2
03/09/14,02:19:31,63.9
03/09/14,02:29:31,65.1
03/09/14,02:39:31,60.3
03/09/14,02:49:31,64.2
03/09/14,02:59:31,59.7
03/09/14,03:09:31,59.1
03/09/14,03:19:31,61
03/09/14,03:29:31,66
03/09/14,03:39:31,63.9
03/09/14,03:49:31,60.2
03/09/14,03:59:31,61.3
03/09/14,04:09:31,63.2
03/09/14,04:19:31,64.9
03/09/14,04:29:31,66
03/09/14,04:39:31,60.5
03/09/14,04:49:31,66.3
03/09/14,04:59:31,62.3
03/09/14,05:09:31,62.3
03/09/14,05:19:31,65.2
03/09/14,05:29:31,63.5
03/09/14,05:39:31,65.2
03/09/14,05:49:31,60.8
03/09/14,05:59:31,62.1
03/09/14,06:09:31,66.6
03/09/14,06:19:31,67.9
03/09/14,06:29:31,64
03/09/14,06:39:31,62.3
03/09/14,06:49:31,62.6
03/09/14,06:59:31,62.5
03/09/14,07:09:31,61.8
03/09/14,07:19:31,60.9
03/09/14,07:29:31,62.7
03/09/14,07:39:31,59.9
03/09/14,07:49:31,59.1
03/09/14,07:59:31,62.6
03/09/14,08:09:31,65.3
03/09/14,08:19:31,58.2
03/09/14,08:29:31,60.8


Thank You,
Natu