R help - Feb 2011 - Average of several line plots

Hi,

I have several data sets which are all approximately within the same values
as each other (both X and Y) and all of these data sets more or less overlap
each other when plotted on the same graph. However, although each data set
varies between approximately the same range, there are vastly different
numbers of data points within each data set (due to the nature of how these
values had to be measured).

Currently, I am trying to figure out a way to produce a graph showing all
these data sets and a line showing the average of all of the data sets.
Given the different number of data points, I can't think of an easy way to
do this.

Can anybody help?

Thanks!
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On 2011-02-02 08:44, mattnixon wrote:
>
> Hi,
>
> I have several data sets which are all approximately within the same values
> as each other (both X and Y) and all of these data sets more or less
overlap
> each other when plotted on the same graph. However, although each data set
> varies between approximately the same range, there are vastly different
> numbers of data points within each data set (due to the nature of how these
> values had to be measured).
>
> Currently, I am trying to figure out a way to produce a graph showing all
> these data sets and a line showing the average of all of the data sets.
> Given the different number of data points, I can't think of an easy way
to
> do this.
Have a look at ?approxfun

Peter Ehlers
>
> Can anybody help?
>
> Thanks!

It is not clear from your message whether these data represent
functions or such. Could you perhaps bring up an example?

I'm guessing each data set contains evaluation points and function
values at those points, and that you would like to plot these
functions and the mean function all on the same graph, is that right?

If the points in the domain differ from each other, it's not as
immediate to build a mean function. A quick recipe would be to use
splinefun on each data set, generate a new grid for the domain,
evaluate each obtained spline on this grid to get new data sets and
build the mean function from there.

But without an example it's really just guessing. Hope this helps anyway.

?splinefun

Best regards,

Eduardo

On Wed, Feb 2, 2011 at 2:44 PM, mattnixon <m.r.nixon at ex.ac.uk>
wrote:
>
> Hi,
>
> I have several data sets which are all approximately within the same values
> as each other (both X and Y) and all of these data sets more or less
overlap
> each other when plotted on the same graph. However, although each data set
> varies between approximately the same range, there are vastly different
> numbers of data points within each data set (due to the nature of how these
> values had to be measured).
>
> Currently, I am trying to figure out a way to produce a graph showing all
> these data sets and a line showing the average of all of the data sets.
> Given the different number of data points, I can't think of an easy way
to
> do this.
>
> Can anybody help?
>
> Thanks!
> --
> View this message in context:
http://r.789695.n4.nabble.com/Average-of-several-line-plots-tp3254850p3254850.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

Hi,

Peter: thank you, I have taken a look at ?approxfun but I'm not sure it does
what I'm after.

Eduardo:

The data doesn't represent functions. Basically the X values represent the
distance across a sample and the Y values are a measure of the colour
intensity at that point across the sample (i.e. a line plot across the
sample). Each data set represents a measurement across a different section
of the sample. All data sets show alternating 'light' and 'dark'
sections,
though the sample isn't perfect so the widths of each section do not
entirely match up from one data set to another. 

The problem comes from the fact that some data sets contain as many as 400
measurements across the sample whereas others contain as few as 150
measurements. This means that measurements do not necessarily occur at the
same value of X on different data sets. Therefore I think I need some way to
average the lines ('of best fit') that each data set creates on the
graph,
rather than averaging the data ponits themselfs as I can't see how I can
take averages/weighted averages of the data points when they occur at
different values of X (and at different intervals) across the sample. Is my
description any better this time?
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