HP 39gs Master Manual page 119

The variable controls the width of the
HWidth
columns, with the initial starting value and
end value set by . In the frequency
HRng
table on the previous page the interval width
was 10. By setting to 10 in the
HWidth
view as shown right we can
PLOT SETUP
produce the graph shown below. Note the changes to and
Xtick Ytick
also.
Centering columns in the histogram
Another use for the variables and is to
HWidth HRng
re-orient the columns so that they are centered on the
data point. For example, the data set below produces
the graph to the right of it using Auto Scale.
You may have noticed that the columns are not centered around the data
points 1, 2 and 3. Instead the columns extend from 1..2, 2..3 and 3..4.
This bothers some people and can easily be fixed by changing the
. If you look at the values you will see that they
HRng PLOT SETUP
are currently set to 1 to 4. This is the default behavior for Auto Scale.
To center the columns you need only change the minimum value for
by subtracting a half column width giving 0.5. The results are
HRng
shown right and you can see that the columns are now centered as
required.
If you want to use linear interpolation to obtain
better values for the median and quartiles then
you can download an aplet from the author's
website called "Grouped Data". This will
calculate the values of the medians and
quartiles using linear interpolation and will also
allow calculations such as "What value will cut off the top 15% of
data?".
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