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From: Niels L. Ellegaard on 3 Jun 2010 12:08

The following is probably a feature request, but maybe someone can help
me find a good work around.

I would like to be able to fit a trend line to a sub interval of a
dataset. So lets say that I have to the following dataset.

x= 1,2,3,4,5,6,7,8,9,10
y= 1,1,1,1,3,5,7,9,9,9

Now I want to draw a scatter plot that contains all the 10 data points,
but the trend line in the scatter plot should only be fitted to
datapoints (x,y) for which x>=4 and x<=8. This feature is be really
useful in high school physics classes because a lot of the time a
mathematical model only fits to a part of the data.

As an example a high school student may heat water in a water cooker and
use termometer connected to a PDA to measure the temperature as a
function of time. If the effect is constant then the temperature will
rise as a linear function of time until the water starts boiling. Then
the temperature curve will level of and be constant. In order to
estimate the heat capacity of water the student needs to fit a trend
line to the data points in time interval where the water has not yet
boiled.

In principle I can solve the problem by creating a figure with two
scatter plots. The first scatter plot contains all the data points,
whereas the second scatter plot only contains data in the chosen
subinterval. This way all the data is visible, but the trend line is
only fitted to data in the subinterval. But this approach is a little
too complicated to be useful.

Ideally the tab named "type" in the popup window for trend lines should
contain two extra options named "xmin" and "xmax". These two options
should determine the interval in which the trend line was fitted. This
feature would make openoffice a more useful tool in high school physics
education.

Is there a simple way to solve this problem? Should I write a feature
request?

Niels




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Prev: OOoCon 2006 - 2009
Next: Fitting a trendline to a subinterval of a dataset.