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Re: reading large multicolumn data file [message #72143 is a reply to message #72136]

Thu, 05 August 2010 20:05

penteado
Messages: 866
Registered: February 2018

Senior Member
Administrator

On Aug 5, 8:54 pm, bio_amateur <hoangtrongminht...@gmail.com> wrote:
> I have a data file (a few hundreds MB). This is a text file in the
> format X Y1 Y2 Y3 (first column is the common x-axis data, next
> columns are data). I can read the data and plot easily with xmgrace
> using
>
> xmgrace -nxy data.dat
>
> which take a few seconds to plot. Now, I want to use IDL to read this
> file and display using iTool. What I did was
>
> data = read_ascii(filename)
> myPlotData = data.(0)
> rows = (size(myPlotData, /dimension))[0]
> for ii=1, rows do begin
> iPlot, myPlotData[0,*], myPlotData[ii,*], /overplot
> end
>
> This method takes so long. Could someone good at this can point out a
> solution for me.

The iTools, as any use of object graphics, can get heavy in memory
when the number of vertices is large (typically, from several hundred
thousand). This may be alleviated if change your IDL preferences to
use hardware rendering, in case it is not already in hardware. Other
than that, only using direct graphics will solve it, as in

minx=min(myplotdata[0,*],max=maxx)
miny=min(myplotdata[1:*,*],max=maxy)

plot,[minx,maxx],[miny,maxy],/nodata
for ii=1,rows-1 do oplot,myplotdata[0,*],myplotdata[ii,*]

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[Message index]

		Re: reading large multicolumn data file By: bio_amateur on Fri, 06 August 2010 11:22
		Re: reading large multicolumn data file By: David Fanning on Fri, 06 August 2010 08:17
		Re: reading large multicolumn data file By: David Fanning on Fri, 06 August 2010 07:46
		Re: reading large multicolumn data file By: bio_amateur on Fri, 06 August 2010 07:23
		Re: reading large multicolumn data file By: bio_amateur on Fri, 06 August 2010 07:23
		Re: reading large multicolumn data file By: penteado on Thu, 05 August 2010 20:05

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