of course, in any 2 dimensional graph ... you are very limited in what you
can do since, you are trying to distinguish between points with identical
coordinates ... ANY sort of an offset system will distort the data ... some
density system in the darkness of the plotting symbol or shade of color
still leaves you not know how many points are at that spot
then you have the problem of trying to differentiate say the X=53.2 and
Y=67.8 (of which there might be 10) from ... an adjacent value of X=53.1
and Y=67.9 ...
good 3 dimensional plots help this a bit but, do not fully get around the
problem ...
i guess i would ask what the purpose is for seeing the plot? if it is to
note a pattern (if there is one) and get a feel for where different
concentrations of data points might be ... then i have found jitter in
minitab to be sufficient (i just wish it were the default mode) ... if you
really want to get REAL accurate .. then one has to sort data on X and see
what happens on Y ...
finally, given that so much of our data has been rounded in some fashion
... getting overly precise with this seems to be trying to make out for our
data ... something that it does not contain
At 09:34 PM 5/29/01 -0400, Peter Nash wrote:
>Do you know any statistical software shows on a scatter-plot when points are
>coincident (i.e. there are numerous points that overlap in one location)?
>This is sometimes shown using jitter, sometimes different sizes for the
>points, sometimes adding leaves to the points to indicate the number of
>overlapping points, and sometimes this can be performed by changing a 2D
>graph to 3D.
>
>This feature is crucial because it IMMEDIATELY shows the importance of the
>points. (Not Minitab, which insists on jittering ALL the plotted points)
>
>
>
>
>
>
>
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_________________________________________________________
dennis roberts, educational psychology, penn state university
208 cedar, AC 8148632401, mailto:[EMAIL PROTECTED]
http://roberts.ed.psu.edu/users/droberts/drober~1.htm
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