Graph Dates and Values

brianrpsgt1 brianlong at cox.net
Tue Mar 10 18:54:57 CET 2009


On Mar 10, 9:44 am, "Gabriel Genellina" <gagsl-... at yahoo.com.ar>
wrote:
> En Tue, 10 Mar 2009 13:32:10 -0200, brianrpsgt1 <brianl... at cox.net>  
> escribió:
>
>
>
>
>
> > On Mar 10, 7:40 am, "Gabriel Genellina" <gagsl-... at yahoo.com.ar>
> > wrote:
> >> En Tue, 10 Mar 2009 05:08:41 -0200, brianrpsgt1 <brianl... at cox.net>  
> >> escribió:
>
> >> > I am trying to plot dates and values on a graph using matplotlib.
> >> > Below is the code.  I can run this and it works great, until I get to
> >> > about 2000 rows from the DB.  Things really start to slow down.  I
> >> > have successfully plotted up to 5000 rows from the DB, but it is very
> >> > slow.  I am attempting to plot values for a day, which would be equal
> >> > to 84600 records.  Is there a more efficient may to accomplish this?
> >> Without looking at the matplotlib docs, the above [] suggests that both  
> >> date2num and plt.plot take a list of values to act upon, and you're  
> >> feeding one point at a time. Probably you end up creating one series  
> >> per  
> >> point (instead of a single series with many points). I guess something  
> >> like this should work:
>
> >> x, y = zip(*value_data) # "transpose"
> >> dates = mdates.date2num(x)
> >> plt.plot(dates, y, 'bo', ms=6)
>
> > Thanks for the notes.  That is exactly what I thought the problem
> > was.  Here is an update.  I put a limit to 100 on the SQL Query to
> > test.  When I run your code, I get the data returned, however, I get
> > the same return equal to the limit I set.  In other words, when I run
> > with a limit of 100, I get the same result 100 times.  Which would
> > mean that when I try to run a whole day (86400 :) - it was late!), I
> > am getting the same result 86400 times and then it is tyring to plot
> > that.
>
> > Output below:
>
> > [ 733414.06489583  733414.06490741  733414.06491898  733414.06493056 ...
> >   733414.06600694  733414.06601852  733414.06603009  733414.06604167]
> > (95, 95, 95, 95, ...  95, 95, 95, 94)
>
> > If I run this code:
>
> > for s in value_data:
> >     x = mdates.date2num([s[0]])
> >     y = [s[1]]
> >     print [x, y]
>
> > The results returned are the following:
>
> > There are 100 rows in the database
> > [ 733414.06489583] [95]
> > [ 733414.06490741] [95]
> > [ 733414.06491898] [95]
> > [ 733414.06493056] [95] ...
> > [ 733414.06600694] [95]
> > [ 733414.06601852] [95]
> > [ 733414.06603009] [95]
> > [ 733414.06604167] [94]
>
> Well, both look the same values to me... what's wrong? Why do you say "the  
> same results 100 times".
>
> Oh, the code fragment I posted is suposed to *replace* the original for  
> loop. Don't put it inside a loop.
>
> --
> Gabriel Genellina

Gabriel ::

Thank you very much!!!  That was it, I had it in the loop.  I works
great now!!  Graphs are coming up right away.

B



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