# [R] OT: compare several graphs

Jan_Svatos@eurotel.cz Jan_Svatos at eurotel.cz
Mon Oct 22 15:30:07 CEST 2001

```Hi Sven,

I am just doing something similar-
my graphs are densities of nonnegative r.v's (with all probability mass at
fixed bounded interval).
Then I compute their "distance" by dist (mva package needed), i.e.

my.dist<-dist(t(cbind(dens1\$y, dens2\$y)))

(provided that dist1\$x==dist2\$x, of course)
The problem of course is, how to decide about statistical and/or
"practical" significance of a difference.
I cannot remain myself of some correct statistical test of such hypothesis

H: f_1 \eqiv f_2 (given that at least the family of f_1, f_2 is known) vs.
H_1: f_1 \neq f_2

The Kolmogorov-Smirnov may be not sensitive to some alternatives.

But still the comparison of (appropriate kernel estimates of) densities may
be of some help.

Jan
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/- Jan Svatos,              Sokolovska 855/225 -/
/- Data Analyst,            Prague 9           -/
/- Eurotel Praha            190 00             -/
/- jan_svatos at eurotel.cz    Czechia            -/
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- - - Original message: - - -
From: owner-r-help at stat.math.ethz.ch
Send: 10/22/01 3:14:11 PM
To: R-Help <r-help at stat.math.ethz.ch>
Subject: [R] OT: compare several graphs

Hi all,

this is OT, but maybe someone can give me a clue. I've got data from eye
tracker experiments (750 data points). These figures show how the data
lock like

|**  *    *****     |***     ******
|  ** ****          |   *   *
|                   |    * *
|                   |     *
|--------------     |---------------

Y axes display velocity, x axes display time, * are the data points. My
question is if there is a method to compare these graphs statistical and
decide if they are different from each other or not. Maybe I can divide
the x axes into several intervals and compare the means?

Thanks for any suggestions,
Sven
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```