Re: [Matplotlib-users] Plotting result of SQL query using pylab "plot"

[Darren D. <dd...@co...>]

On Wednesday 04 May 2005 12:54 pm, Michael J. Rehberg wrote:
> Hello list,
>
> So far I'm pleased with matplotlib and python.  I'm a pretty new user and
> find the coding very rapid and the ability to glue different database and
> statistical programs together pretty slick.  I have a question.
>
> I am retrieving data from a database using an ODBC connection.  When I
> print the result set, "sql_result_set", looks like this, a list of tuples
> (I think?):
>
>     [(31773, 60.691), (31772, 61.991), ...and so on... (31774, 60.779)]
>
> Each tuple contains the X value and Y value for each coordinate on the line
> plot I wish to make.
>
> After experimentation, I found that I could extract 2 vectors, one for x
> and one for y, by doing this:
>
>     x_value = [thisrow[0] for thisrow in sql_result_set]
>     y_value = [thisrow[1] for thisrow in sql_result_set]
>
> and then fed the result into plot
>
>     plot(x_value, y_value)
>
> Now this works, but seems an inefficient way to do this.
>
> Is there a way to force the plot(x,y) command to recognize my
> "sql_result_set" as a list of x,y tuples, instead of splitting the set into
> two vectors?  This would seem a natural way for plot to operate.  Somehow I
> think the "apply" notation, "*" or "**", might do this, but I'm stuck.
>
> Thanks for your ideas.  Please let me know if I missed the obvious.

Hi Michael,

You can use a LineCollection for this. Check out line_collections.py in the 
examples directory (in CVS, not included with mpl-0.80).

Darren

-- 
Darren S. Dale

Bard Hall
Department of Materials Science and Engineering
Cornell University
Ithaca, NY. 14850

dd...@co...