Re: Histogram chart - What do the y-axis numbers mean?
- From: Jean Bréfort <jean brefort normalesup org>
- To: Marlon Nelson <marlon nelson gmail com>
- Cc: gnumeric-list gnome org
- Subject: Re: Histogram chart - What do the y-axis numbers mean?
- Date: Fri, 12 Sep 2008 22:19:22 +0200
Le vendredi 12 septembre 2008 à 15:28 -0400, Marlon Nelson a écrit :
Thank you, Jean
Another question: The data table was produced using the Histogram
tool. The 1% bin counts 1011 data points between -1% and 1%. In the
chart of the histogram, the area representing those points falls
between 1% and 3% on the x-axis. Seems like an off-by-one problem to
me.
The histogram plot needs one more x data than y data the first y data is
assumed to represent the number of occurences between the two first x
data. I have plans to implement hidtograms from raw data at some moment
in the future.
Regards,
Jean
On Fri, Sep 12, 2008 at 11:17 AM, Jean Bréfort <jean brefort free fr> wrote:
Le vendredi 12 septembre 2008 à 10:46 -0400, Marlon Nelson a écrit :
I originally thought this was a bug and was about 30 seconds from
submitting one to bugzilla when I began to suspect the problem is with
my understanding of what a histogram is.
With the data listed below (frequency of daily returns of Merrill
Lynch stock over the last 10 years), I created a histogram chart. The
highest point on the chart reaches 50,000. I was expecting 1011.
Reading a bit from wikipedia, I see what I was actually expecting to
see is a bar chart.
But given a histogram chart of this data, what do the y-axis numbers mean?
Bin Frequency
-15% 1
-13% 1
-11% 4
-9% 6
-7% 13
-5% 53
-3% 167
-1% 510
1% 1011
3% 489
5% 156
7% 57
9% 26
11% 6
13% 4
15% 3
17% 2
--
-eom-
The histogram plots the density, as the 1011 data are in a 0.02
interval, you get 1011 / 0.02 = 50550 as the largest value.
Regards,
Jean
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