On Wed, 4 Apr 2012 10:59:20 -0500, "Jay A. Kreibich"
wrote:
> Not to mention avg().
>
> You might want to have a look at how RRDtool deals with condensing
> data. It is common pratice to plot average, min, and max to preserve
> outliers, while still showing trends.
>
> http://oss.oetiker.c
On Wed, Apr 04, 2012 at 12:05:44PM +0200, Steinar Midtskogen scratched on the
wall:
> [Jean-Christophe Deschamps]
>
> > You're going to have at most one random sample in every slice of 320
> > s. The GROUP BY clause will select only one for you and the query can
> > be as simple as:
> >
> > sele
Let's say that I want to plot the entire column and the plot is 1000
pixels wide. Then I only need 1000 samples, so I could do this:
SELECT timestamp, sample FROM mytable GROUP BY timestamp * 1000 / ((SELECT
max(timestamp) FROM mytable) - (SELECT min(timestamp) FROM mytable));
(timestamp is the
[Jean-Christophe Deschamps]
> You're going to have at most one random sample in every slice of 320
> s. The GROUP BY clause will select only one for you and the query can
> be as simple as:
>
> select sample from from mytable group by timestamp / 320 order by
> timestamp;
Ah. I didn't think of
This is a good suggestion. A drawback is that the interval can't be
too small otherwise there is a risk that a sample would be missed. So
I will get more samples than I need. In you example, if there is a
sample every second more or less, I would usually get 3-4 samples
every hour instead of
[Jean-Christophe Deschamps]
>>If your sampling is essentially regular, why not make it
>>
>>select ... where timestamp % N between min_interval and max_interval
>>
>> N being the typical time delta of your n rows above and interval
>> bounds reducing the possiblity of gross under- and over-samplin
Hit Send inadvertandly, sorry.
My rowid isn't increasing with something predictable, so I can't do
something like WHERE rowid % n = 0. I can use WHERE random() % n = 0
giving me sort of what I want (better than row % n, but I still need
something better).
If your sampling is essentially regul
I have a big database with timestamps and sensor readings, which I
access with SELECT to have gnuplot draw graphs. However, sometimes I
have readings every minute and want to plot several years of data, and
feeding everything to gnuplot is overkill. In these cases it would be
sufficient to sel
I have a big database with timestamps and sensor readings, which I
access with SELECT to have gnuplot draw graphs. However, sometimes I
have readings every minute and want to plot several years of data, and
feeding everything to gnuplot is overkill. In these cases it would be
sufficient to select
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