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Re: matching fields in ascii or text files.
Patrick McEnaney wrote:
> "Pavel A. Romashkin" <firstname.lastname@example.org> wrote in message news:<3B6AD991.5669DE2B@noaa.gov>...
> > Are you attempting this in IDL? Or is it a general data handling
> > question? It seems to me that TXT file and ASCII is the same kind of
> > file. To compare the columns by scrolling them in a window, Excel will do.
> > Cheers,
> > Pavel
> Greetings Pavel-
> I'm writing an idl gui script to cycle through fairly long files of
> data that are collected from a ctd and compare them with chlorophyll
> measurements from insitu sampling. I want to select the data from a
> specific depth for chlorophyll and and write all values for that
> depth in another file. Just putting the data into excel files would be
> very cumbersome because the data are collected over a month long
> cruise and there are alot of measurements. Ultimately I'll use the
> script whenever I need to compare fields from cruise data. Can you
> suggest a way to construct such a matching routine in idl?
The first question that came to my mind (apart from "aren't TXT and ASCII the same thing?"
:o) was: what do you mean by compare? Do you have a depth tolerance? e.g. given a depth
value from one file is +/- 10m from another file considered the "same" depth?
Also when you said:
"I want to select the data from a specific depth for chlorophyll and and write all values
for that depth in another file."
did you mean:
"I want to select the data from a specific depth for chlorophyll and write all **the ctd**
values for that depth in another file."
My first cut at something like this would be to pick the dataset with the least number of
depth values, say the chlorophyll stuff - you can loop through those depths. Then you can
use where to find the corresponding depths for the ctd data, like:
IDL> ctd_depth = findgen(10000)/100. & chlorophyll_depth = 20.0
IDL> help, ctd_depth, chlorophyll_depth
CTD_DEPTH FLOAT = Array
FLOAT = 20.0000
IDL> depth_tolerance=0.1 ; metres, for example
IDL> loc = where( abs(ctd_depth-chlorophyll_depth) lt depth_tolerance, count )
and loc should give those ctd_depths that are within your tolerance for matching
IDL> print, ctd_depth[loc]
19.9100 19.9200 19.9300 19.9400 19.9500
19.9600 19.9700 19.9800 19.9900 20.0000
20.0100 20.0200 20.0300 20.0400 20.0500
20.0600 20.0700 20.0800 20.0900
adn then write all the data asociated with those ctd depths (using loc) to another file.
Is this the sort of thing you mean?? If so, why would you need a gui?
p.s. If you have to read in simple columnar ASCII data files (that just contain numbers),
you might want to have a look at DDREAD.PRO - it's a piece of IDL code (written by a
feller called Fred Knight) that I find indispensible for simply reading in column ASCII
Paul van Delst A little learning is a dangerous thing;
CIMSS @ NOAA/NCEP Drink deep, or taste not the Pierian spring;
Ph: (301)763-8000 x7274 There shallow draughts intoxicate the brain,
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