histplot

Scilab Function
Last update : 17/05/2005

histplot - plot a histogram

### Calling Sequence

  `histplot(n, data, <opt_args>)`
  `histplot(x, data, <opt_args>)`

### Parameters

- `n`: positive integer (number of classes)
- `x`: increasing vector defining the classes (`x` may have at least 2 components)
- `data`: vector (datas to be analysed)
- `<opt_args>`: This represents a sequence of statements `key1=value1,key2=value2` ,... where `key1`, `key2,...` can be any optional `plot2d` parameter (`style,strf,leg, rect,nax, logflag,frameflag, axesflag`) or normalization. For this last one the corresponding value must be a boolean scalar (default value %t).

### Description

This function plot an histogram of the `data` vector using the classes `x`. When the number `n` of classes is provided instead of `x`, the classes are choosen equally spaced and x(1) = min(data) < x(2) = x(1) + dx < ... < x(n+1) = max(data) with dx = (x(n+1)-x(1))/n.

The classes are defined by C1 = [x(1), x(2)] and Ci = ( x(i), x(i+1)] for i >= 2. Noting Nmax the total number of `data` (Nmax = length(data)) and Ni the number of `data` components falling in Ci, the value of the histogram for x in Ci is equal to Ni/(Nmax (x(i+1)-x(i))) when `normalization` is true (default case) and else, simply equal to Ni. When normalization occurs the histogram verifies:

                x(n+1)
               /
               |   h(x) dx = 1,  when x(1)<=min(data) and max(data) <= x(n+1))
               /
               x(1)

Any `plot2d` (optional) parameter may be provided; for instance to plot an histogram with the color number 2 (blue if std colormap is used) and to restrict the plot inside the rectangle [-3,3]x[0,0.5], you may use `histplot(n,data, style=2, rect=[-3,0,3,0.5])`.

Enter the command `histplot()` to see a demo.

### Examples

    // example #1: variations around an histogram of a gaussian random sample
    d=rand(1,10000,'normal');  // the gaussian random sample
    clf();histplot(20,d)
    clf();histplot(20,d,normalization=%f)
    clf();histplot(20,d,leg='rand(1,10000,''normal'')',style=5)
    clf();histplot(20,d,leg='rand(1,10000,''normal'')',style=16, rect=[-3,0,3,0.5]);

    // example #2: histogram of a binomial (B(6,0.5)) random sample
    d = grand(1000,1,"bin", 6, 0.5);
    c = linspace(-0.5,6.5,8);
    xbasc()
    subplot(2,1,1)
       histplot(c, d, style=2)
       xtitle("normalized histogram")
    subplot(2,1,2)
       histplot(c, d, normalization=%f, style=5)
       xtitle("non normalized histogram")

    // example #3: histogram of an exponential random sample
    lambda = 2;
    X = grand(100000,1,"exp", 1/lambda);
    Xmax = max(X);
    xbasc()
    histplot(40, X, style=2)
    x = linspace(0,max(Xmax),100)';
    plot2d(x,lambda*exp(-lambda*x),strf="000",style=5)
    legend(["exponential random sample histogram" "exact density curve"]);
    // Note: if you use the old graphic mode use instead
    // legends(["exponential random sample histogram" "exact density curve"],[2 5],"ur");

### See Also

`hist3d`, `plot2d`, `dsearch`,