Re: [Matplotlib-users] Eye patterns (Heat plot?)

[Benjamin R. <ben...@ou...>]

On Mon, Jan 23, 2012 at 1:46 PM, Ethan Swint <es...@vt...> wrote:

>
>
> On 1/23/2012 1:55 PM, Russ Dill wrote:
> > On Mon, Jan 23, 2012 at 11:17 AM, Stan West<sta...@nr...>
>  wrote:
> >>> From: Russ Dill [mailto:rus...@gm...]
> >>> Sent: Saturday, January 21, 2012 16:31
> >>>
> >>> I'm using matplotlib from pylab to generate eye patterns for signal
> >>> simulations.
> >> ...
> >>
> >>> Is there any way within matplotlib to do that right now?
> >> One way combines Numpy's histogram2d and matplotlib's imshow, as in the
> >> example in the histogram2d docs [1].  The example's x array should
> become all
> >> of the time samples in your traces, strung together in one dimension;
> the y
> >> array, the corresponding voltage samples.
> >>
> > I'll try it out and see what I get, but I don't think it will work so
> > well. The problem is that while the data is made up of x/y samples, it
> > actually represents a line. The samples should be evenly distributed
> > not along the x or y axis, but along the length of the line. I feel
> > like I'll need a line drawing algorithm.
> >
> > (For example, if samples are evenly distributed along the x axis, a 89
> > degree line is highly under-represented, but a 1 degree line is highly
> > over-represented. The number of samples should be sqrt(dx^2 + dy^2),
> > but with evenly spaced x samples, its just dx.
>
> I don't know of a way to directly produce the LeCroy heatmap in Python,
> so here's my idea for a hack:
> *Each sample point you have from the trace represents a point in XY
> coordinates.
> *Similarly, the plot area is filled with regularly spaced XY coordinates.
> *Every trace sample will fall within a square bounding box with four
> points.
> *Each plot area point gets a membership value, based on distance between
> centers of the sample point and the plot area point.
> *To construct the heat diagram, sum the membership values of all sample
> points for all traces.
> *Display it with a contour plot, but without the isovalue lines.
>
> -Ethan
>
>
matplotlib also has hexbin() if that helps.

http://matplotlib.sourceforge.net/api/axes_api.html?highlight=hexbin#matplotlib.axes.Axes.hexbin

Ben Root