Re: Histogram chart - What do the y-axis numbers mean?



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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