# [Numpy-discussion] Simple question about scatter plot graph

josef.pktd at gmail.com josef.pktd at gmail.com
Wed Oct 31 21:12:19 EDT 2012

```On Wed, Oct 31, 2012 at 8:59 PM, klo uo <klonuo at gmail.com> wrote:
> Thanks for your reply
>
> I suppose, variable length signals are split on equal parts and dominant
> harmonic is extracted. Then scatter plot shows this pattern, which has some
> low correlation, but I can't abstract what could be concluded from grid
> pattern, as I lack statistical knowledge.
> Maybe it's saying that data is quantized, which can't be easily seen from
> single sample bar chart, but perhaps scatter plot suggests that? That's only
> my wild guess

http://pandasplotting.blogspot.ca/2012/06/lag-plot.html
In general you would see a lag autocorrelation structure in the plot.

My guess is that even if there is a pattern in your data we might not
see it because we don't see plots that are plotted on top of each
other. We only see the support of the y_t, y_{t+1} transition (points
that are at least once in the sample), but not the frequencies (or
conditional distribution).

If that's the case, then
reduce alpha level so many points on top of each other are darker, or
colorcode the histogram for each y_t: bincount for each y_t and
normalize, or use np.histogram directly for each y_t, then assign to
each point a colorscale depending on it's frequency.

Did you calculate the correlation? (But maybe linear correlation won't
show much.)

Josef

>
>
>
> On Thu, Nov 1, 2012 at 1:17 AM, <josef.pktd at gmail.com> wrote:
>>
>> I don't have much of an idea what we are supposed to see, except that
>> there might not be much autocorrelation.
>>
>> Is this grided data and some scatter points might actually be many points
>> on top of each other so we don't see all points and not the frequencey
>> distribution?
>> Is y on a continuous, metric scale or are all grid points different
>> categories, observations.
>
>
>
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```

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