[gdal-dev] gdal_calc.py: produce median raster

[Marius Jigmond]

That's because numpy.median expects one array and keyword arguments, not three arrays. It's unclear to me what gdal_calc.py does under the hood (I admit I did not read it) but the correct way to get the median of the three bands would be:
--calc median([A,B,C], 0)
The strange part is that--calc median([A,B,C])works as well and generates a different output. When axis is not specified median should return a single value. At this point I suggest you take three 2D arrays, calculate their median as a 2D array, convert the three arrays to rasters, run gdal_calc.py and compare results.
-marius

Date: Tue, 25 Nov 2014 17:56:46 +0900
From: simlangen at gmail.com
To: chris.yesson at ioz.ac.uk
CC: gdal-dev at lists.osgeo.org
Subject: Re: [gdal-dev] gdal_calc.py: produce median raster

Dear Dr Chris Yesson

Thanks for your quick response.

I got the following error:

ValueError: The truth value of an array with more than one element is ambiguous. 
Use a.any() or a.all()`

Perhaps the expression for calc seems to be revised...

On Tue, Nov 25, 2014 at 4:59 PM, Chris Yesson <chris.yesson.phd at gmail.com> wrote:
Dear Simen,
You can refer to each band explicitly using the --A_band option.Try something like this
gdal_calc.py -A infile --A_band 1 -B infile --B_band 2 -C infile --C_band 3  --outfile outfile --calc median(A,B,C)
- ChrisDr Chris Yesson
Institute of Zoology, Zoological Society of LondonTel: 020 7449 6267
email: chris.yesson at ioz.ac.uk
web: http://www.zsl.org/chrisyesson/

Note: I work Mon-Thurs and do not check email on Fri


On 25 November 2014 at 07:44, Simen Langseth <simlangen at gmail.com> wrote:
Dear Respected Authors:
I would be grateful if you could share any hints on it.

On Tue, Nov 25, 2014 at 4:33 PM, Simen Langseth <simlangen at gmail.com> wrote:
Dear Marius Jigmond:

Thanks for your attempt.

Unfortunately, it is producing 3 band outfile, rather than 1 band median image.

I could not figure out what this code computed, all the resulted 3 bands images are also different.

I hope someone can help me.

On Tue, Nov 25, 2014 at 12:09 PM, Marius Jigmond <mariusjigmond at hotmail.com> wrote:



Does the following work:
gdal_calc.py -A infile --allBands=A --outfile=outfile --calc="median(A)"

Date: Mon, 24 Nov 2014 19:14:06 +0900
From: simlangen at gmail.com
To: gdal-dev at lists.osgeo.org
Subject: [gdal-dev] gdal_calc.py: produce median raster

I have one GeoTiff file with 3 bands. I want to produce a raster file computing pixel wise median value for the three raster bands. How can I do that?
I tried as follows:
gdal_calc.py -A infile --allBands --outfile outfile --calc median(A)
But could not get any out file.
 

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