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skipping values in a data file

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  skipping values in a data file "hugocoolens@gmail.com" <hugocoolens@gmail.com> - 2017-06-01 08:47 -0700
    Re: skipping values in a data file Ethan A Merritt <sfeam@users.sourceforge.net> - 2017-06-01 14:26 -0700
      Re: skipping values in a data file "hugocoolens@gmail.com" <hugocoolens@gmail.com> - 2017-06-02 02:39 -0700
        Re: skipping values in a data file Ethan A Merritt <sfeam@users.sourceforge.net> - 2017-06-02 13:25 -0700
          Re: skipping values in a data file "hugocoolens@gmail.com" <hugocoolens@gmail.com> - 2017-06-03 11:31 -0700

#3655 — skipping values in a data file

I have a data file with measurements, each measurement has been repeated 5 times. However because of a bug in the apparatus software the first and the second measurement are always unreliable, therefore I want to skip them
i.e. I don't want to plot these unreliable data points, neither do I want to use them for fitting to a function.
This is an example:
1 #unreliable
1.5 #unreliable
3 #reliable
3.1 #reliable
2.9 #reliable
#start of next 5 measurements:
3 #unreliable
3.1 #unreliable
3.5 #reliable
3.4 #reliable
3.6 #reliable

Can anyone here show me how to do is from within Gnuplot?

kind regards,
Hugo

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#3656

hugocoolens@gmail.com wrote:

> I have a data file with measurements, each measurement has been repeated 5
> times. However because of a bug in the apparatus software the first and
> the second measurement are always unreliable, therefore I want to skip
> them i.e. I don't want to plot these unreliable data points, neither do I
> want to use them for fitting to a function. This is an example: 1
> #unreliable 1.5 #unreliable 3 #reliable
> 3.1 #reliable
> 2.9 #reliable
> #start of next 5 measurements:
> 3 #unreliable
> 3.1 #unreliable
> 3.5 #reliable
> 3.4 #reliable
> 3.6 #reliable
> 
> Can anyone here show me how to do is from within Gnuplot?
> kind regards,
> Hugo

If it is always the first two measurements in the file, you can add "skip 2"
to the plot or fit statement:

    plot "foo" skip 2 using 0:1

However your sample above seems to show that that there are multiple blocks
of data in the file and in each block the first 2 records are bad.
For this you could instead use

    plot "foo" every ::2 using 0:1

But note that you need a blank line between the data blocks for this to work
(otherwise gnuplot does not know that new block of data is starting).

See "help every"

	Ethan
 

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#3659

Op donderdag 1 juni 2017 23:26:46 UTC+2 schreef Ethan A Merritt:
> hugocoolens@gmail.com wrote:
> 
> > I have a data file with measurements, each measurement has been repeated 5
> > times. However because of a bug in the apparatus software the first and
> > the second measurement are always unreliable, therefore I want to skip
> > them i.e. I don't want to plot these unreliable data points, neither do I
> > want to use them for fitting to a function. This is an example: 1
> > #unreliable 1.5 #unreliable 3 #reliable
> > 3.1 #reliable
> > 2.9 #reliable
> > #start of next 5 measurements:
> > 3 #unreliable
> > 3.1 #unreliable
> > 3.5 #reliable
> > 3.4 #reliable
> > 3.6 #reliable
> > 
> > Can anyone here show me how to do is from within Gnuplot?
> > kind regards,
> > Hugo
> 
> If it is always the first two measurements in the file, you can add "skip 2"
> to the plot or fit statement:
> 
>     plot "foo" skip 2 using 0:1
> 
> However your sample above seems to show that that there are multiple blocks
> of data in the file and in each block the first 2 records are bad.
> For this you could instead use
> 
>     plot "foo" every ::2 using 0:1
> 
> But note that you need a blank line between the data blocks for this to work
> (otherwise gnuplot does not know that new block of data is starting).
> 
> See "help every"
> 
> 	Ethan

Thanks a lot for the reply. Adding an extra blank line is no too difficult. Can I also use the "every" syntax in a fit statement? Could you provide an example?

kind regards,
Hugo

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#3661

hugocoolens@gmail.com wrote:

> Op donderdag 1 juni 2017 23:26:46 UTC+2 schreef Ethan A Merritt:
>> hugocoolens@gmail.com wrote:
>> 
>> > I have a data file with measurements, each measurement has been
>> > repeated 5 times. However because of a bug in the apparatus software
>> > the first and the second measurement are always unreliable, therefore I
>> > want to skip them i.e. I don't want to plot these unreliable data
>> > points, neither do I want to use them for fitting to a function. This
>> > is an example: 1
>> > #unreliable 1.5 #unreliable 3 #reliable
>> > 3.1 #reliable
>> > 2.9 #reliable
>> > #start of next 5 measurements:
>> > 3 #unreliable
>> > 3.1 #unreliable
>> > 3.5 #reliable
>> > 3.4 #reliable
>> > 3.6 #reliable
>> > 
>> > Can anyone here show me how to do is from within Gnuplot?
>> > kind regards,
>> > Hugo
>> 
>> If it is always the first two measurements in the file, you can add "skip
>> 2" to the plot or fit statement:
>> 
>>     plot "foo" skip 2 using 0:1
>> 
>> However your sample above seems to show that that there are multiple
>> blocks of data in the file and in each block the first 2 records are bad.
>> For this you could instead use
>> 
>>     plot "foo" every ::2 using 0:1
>> 
>> But note that you need a blank line between the data blocks for this to
>> work (otherwise gnuplot does not know that new block of data is
>> starting).
>> 
>> See "help every"
>> 
>> Ethan
> 
> Thanks a lot for the reply. Adding an extra blank line is no too
> difficult. Can I also use the "every" syntax in a fit statement? 

Yes.  "plot" and "fit" both use exactly the same data input stage.

> Could you provide an example?

One of the examples in the fit demo uses "every 5" to select points
   http://gnuplot.sourceforge.net/demo_cvs/fit.html

The demo "matrix_every.dem" may also be helpful (it's in the distributed
demo collection but not one of the on-line examples).

	Ethan

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#3662

Op vrijdag 2 juni 2017 22:25:31 UTC+2 schreef Ethan A Merritt:
> hugocoolens@gmail.com wrote:
> 
> > Op donderdag 1 juni 2017 23:26:46 UTC+2 schreef Ethan A Merritt:
> >> hugocoolens@gmail.com wrote:
> >> 
> >> > I have a data file with measurements, each measurement has been
> >> > repeated 5 times. However because of a bug in the apparatus software
> >> > the first and the second measurement are always unreliable, therefore I
> >> > want to skip them i.e. I don't want to plot these unreliable data
> >> > points, neither do I want to use them for fitting to a function. This
> >> > is an example: 1
> >> > #unreliable 1.5 #unreliable 3 #reliable
> >> > 3.1 #reliable
> >> > 2.9 #reliable
> >> > #start of next 5 measurements:
> >> > 3 #unreliable
> >> > 3.1 #unreliable
> >> > 3.5 #reliable
> >> > 3.4 #reliable
> >> > 3.6 #reliable
> >> > 
> >> > Can anyone here show me how to do is from within Gnuplot?
> >> > kind regards,
> >> > Hugo
> >> 
> >> If it is always the first two measurements in the file, you can add "skip
> >> 2" to the plot or fit statement:
> >> 
> >>     plot "foo" skip 2 using 0:1
> >> 
> >> However your sample above seems to show that that there are multiple
> >> blocks of data in the file and in each block the first 2 records are bad.
> >> For this you could instead use
> >> 
> >>     plot "foo" every ::2 using 0:1
> >> 
> >> But note that you need a blank line between the data blocks for this to
> >> work (otherwise gnuplot does not know that new block of data is
> >> starting).
> >> 
> >> See "help every"
> >> 
> >> Ethan
> > 
> > Thanks a lot for the reply. Adding an extra blank line is no too
> > difficult. Can I also use the "every" syntax in a fit statement? 
> 
> Yes.  "plot" and "fit" both use exactly the same data input stage.
> 
> > Could you provide an example?
> 
> One of the examples in the fit demo uses "every 5" to select points
>    http://gnuplot.sourceforge.net/demo_cvs/fit.html
> 
> The demo "matrix_every.dem" may also be helpful (it's in the distributed
> demo collection but not one of the on-line examples).
> 
> 	Ethan

Thanks a lot for pointing me to the example
Kind regards,
Hugo

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