Re: Histogram Functions
- From: mees <m_oylulan@xxxxxxxxxxx>
- Date: Wed, 24 Aug 2005 08:38:02 -0400
NZTideMan wrote:
>
>
> I don't understand why your being new to Matlab should make hist
> difficult.
> I haven't looked at the details of hist, but I assume it does
> something
> like this:
> 1. Sort the data into ascending order
> 2. Count the number of data that fall into each bin (either defined
> by
> the user or assumed to be equispaced from min to max.)
>
> You could code this up yourself.
> All hist is is a shortcut for you, to save you the time coding it.
> If you don't understand how to use it, you should make your own
> hist to
> do exactly what you want to achieve.
> That's what you as a novice needs to learn, i.e., there's nothing
> magic
> about commands like hist or mean or kurtosis. They're just a
> shortcut.
> You could code them yourself.
>
>
Hi,
A histogram is a graph that shows how frequently a particular 'event'
occurs. Say you have a town with
a population of 50,000 and you want to figure out
the age distribution of the inhabitants. To use the
hist function you would need two set of data:
1.
A vector of length 50,000 containing the age of each
person.
age = [age_data_goes_here];
2.
A vector of bins defining the age categories e.g. in age intervals of
15 yrs, beginning at 0yrs and ending at 100yrs:
bin = [0:15:100];
3.
With this data the following command in MATLAB:
hist(bin, age)
should plot a bar graph with the age categories on the
x-axis and the number of people in that age category on
the y-axis.
If you did not specify the bin sizes and just typed the command:
hist(age)
MATLAB would plot the data with 10 bin intervals divided equally
between the highest and lowest ages that occurred in the age[] vector
above.
In the MATLAB function online help pages, one of the examples defines
the vector of input data (analogous to the age vector above) as a
random vector y of 10,000 elements:
y = randn(10000,1);
The bins are defined by a vector x with intervals of 0.1 in the range
-2.9 to 2.9:
x = -2.9:0.1:2.9;
Hope this helps!
M
.
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