Hei Rajat,
I assume you have two files in your working directory: NDVIFILES and VIQALIST
cat NDVIFILES
NDVI_332.tif
NDVI_241.tif
NDVI_001.tif
...
cat VIQALIST
VIQA_332.tif
VIQA_241.tif
VIQA_001.tif
...
Then this line of code should do what you want:
paste -d ' ' VIQALIST NDVIFILES | awk '{print "expression=\"NDVI_QA_"
substr($1,6,3) "=" $2 " * " $1 "\""}' | xargs -P2 -I{} r.mapcalc {}
Some explanation:
For using paste the order is important, because the paste command concatenates
line 1 from file 1 with line 1 from file 2, line 2 from file 1 with line 2 from
file 2 and so on. So, please double check that the order of the maps in both
lists match (if not, use sort or something).
awk is very handy for table like text files / data. By default it assumes
"space" as delimiter for columns. $1 refers to column 1, $2 refers to column 2
(and $0 would refer to the whole). In the example awk is used to generate a
map calculator expression from the two files merged with "paste".
substr($1,6,3) extracts the file number (3 letters starting with position 6)
from the map names of the maps listed in file 1. I recommend having a look at
one of the many awk tutorials online.
xargs is a tool for executing commands in parallel. -P2 means that 2 cores are
used, if you have more on your system you can increase the number of cores
used.-I{} says that the string {} is replaced by the text is being piped to
xargs (you could use othe strings if you like to).
Hope that helps.
Cheers
Stefan
From: Rajat Nayak [mailto:rajat27...@gmail.com]
Sent: 5. april 2014 03:38
To: Blumentrath, Stefan
Subject: Re: [GRASS-user] looping r.mapcalc in a shell script
Dear Stefan,
I have attached a few files for your reference with this mail. There are 3
files for NDVI and 3 for QA. In GRASS 7 I created NDVILIST and QALIST with NDVI
and all QA files (each with 23 files for my analysis) respectively using
g.mlist.
I'm presently running on ubuntu 12.04.
Hope this helps,
Thanking you,
Regards,
Rajat
Rajat Nayak
On Fri, Apr 4, 2014 at 2:21 PM, Blumentrath, Stefan
<stefan.blumentr...@nina.no<mailto:stefan.blumentr...@nina.no>> wrote:
Hi Rajat,
If you send me your two files I can send you a line of code that should work.
In this case I will need to know if you work with GRASS 6 or 7 and your
operating system...
Cheers
Stefan
From: Rajat Nayak [mailto:rajat27...@gmail.com<mailto:rajat27...@gmail.com>]
Sent: 4. april 2014 04:47
To: Blumentrath, Stefan
Subject: Re: [GRASS-user] looping r.mapcalc in a shell script
Thank you Stefan for your reply.
One of the problems I'm facing with all the suggested codes is, the code is
unable to find either of the file lists.
Both the filelists were created using g.mlist command, it it worked fine with
other loops like reclass.
I will work again on your suggested line of thoughts, and hope will be able to
crack it.
Regards
Rajat
Rajat Nayak
On Thu, Apr 3, 2014 at 5:38 PM, Blumentrath, Stefan
<stefan.blumentr...@nina.no<mailto:stefan.blumentr...@nina.no>> wrote:
You could also combine your two lists using the "paste" command, then "awk" in
order to create proper map calculator expressions, which you then can send to
the map calculator through "xargs".
That way you could process the maps in parallel (if you are on a 64bit system
with multi cores)...
Something like (would likely require some adjustments, e.g. regarding field
delimiters):
paste NDVIFILES VIQALIST | awk '{print \" $1 "_MASK"=$1 '" * " $2 \"}' | xargs
-P 4 r.mapcalc {}
Cheers
Stefan
-----Original Message-----
From:
grass-user-boun...@lists.osgeo.org<mailto:grass-user-boun...@lists.osgeo.org>
[mailto:grass-user-boun...@lists.osgeo.org<mailto:grass-user-boun...@lists.osgeo.org>]
On Behalf Of rajatrn
Sent: 3. april 2014 10:31
To: grass-user@lists.osgeo.org<mailto:grass-user@lists.osgeo.org>
Subject: [GRASS-user] looping r.mapcalc in a shell script
Hi,
I have two layer lists, NDVIFILES and VIQALIST, both developed using g.mlist
command in GRASS.
Each file has 22 items in it. I would like to perform a simple raster
calculation of the following form, Mask$NDVIFILES [i] = NDVIFILES[i] *
VIQALIST[i] I'm unable to create a loop which can sequentially produce the
required outputs.
I will be grateful if anyone can help me with creating a loop using bash/shell
script.
I know it is simpler to do it in R but will be great if can be implemented on
using grass terminal/shell.
Thank you in advance,
Sincerely,
Rajat
--
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