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Re: [Discuss-gnuradio] Saving data

From: Marcus Müller
Subject: Re: [Discuss-gnuradio] Saving data
Date: Wed, 21 Oct 2015 12:21:33 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0

Hi Pedro,

you sent a very similar email with exactly the same subject on the 15th of October, and I did my best to help you there (email from back then below). Has my mail gotten lost in spam? Is there some further help you'd need? Did I upset you somehow?

Best regards,

On 16.10.2015 15:01, Marcus Müller wrote:
Hi Pedro,

that's what the file sink is for -- "sinking" data into files.
It's not producing a text file, because text files are pretty much a bad format for floating point values, usually, because you'd either be wasting enormous amounts of storage space to save each number in a textual format that tries as good as possible to represent the floating point value, or you'd lose accuracy. Either way, converting the in-memory binary floats to text is CPU-intense and therefore usually not done, unless you really know that you need it. Even then, it's pretty reasonable to argue that, yes, although
is human-readable, having a million of these lines (and that's how I read "a lot of samples" that you mention) makes the data de-facto unreadable, not even mentioning navigatable, without graphical aids.

Most people just import there samples later on e.g. into matlab -- but you wouldn't want to have textual numbers then, either (Matlab and Octave, as much as Python/numpy, and GNUplot can read binaries like the files produces by file sink directly).

That being said, you can actually pretty simply convert the binary files produced by file sink to text using python. For example, save the following as a text file and run it as "python <name_of_scriptfile> <input_samples.dat> <output_samples.txt>" (untested, since written for this mail only):

import numpy as np
from sys import argv
#complex64: 32bit float real, 32bit float imag
#float32: as name suggests
#int16: short int
format = np.complex64
data = "" dtype=format)
data.tofile(argv[2], sep='\n')

On 20.10.2015 20:22, Pedro Gabriel Adami wrote:
Dear all,

I'm developing a project based in gnuradio and I have to save some data that I get at the end of my flowgraph. I'm using a Number Sink to see the value of the sum I'm making, and I need to analyse these numbers.
Does anyone know how to storage/save this kind of information? It would be great if these numbers were saved in a text file (.txt). Anyway, now I just need to save them (no matter the way), so I can analyse them e take my conclusions.

Thanks a lot.

Pedro Gabriel Adami
Graduando do 4º período de Engenharia de Controle e Automação no Inatel

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