tabul - frequency of values of a matrix or vector

### Calling Sequence

  `[m]=tabul(X [,order])`

### Parameters

- `X` : vector or matrix (of real or complex numbers or strings)
- `order` : (optionnal) a character equal to "d" or "i" (default value "d")
- `m` : a 2 columns matrix (if `X` is a numerical vector or matrix) or a list with 2 members (if `X` is a string vector or matrix).

### Description

This function computes the frequency of values of the components of a vector or matrix `X` of numbers or string characters :

  if X is a numerical vector or matrixthen `m` is a two column matrix who contains in the first column the distinct values of `X` and in the other column the number of occurrences of those values (m(i,2) is the number of occurrences of m(i,1)).
  if X is a string vector or matrixthen `m` is a list whose first member is a string (column) vector composed with the distinct values of `X` and the second member is a (column) vector whose components are the number of occurrences of those values ( m(i)(2) is the number of occurrences of the string m(i)(1) ).

The optional parameter `order` must be "d" or "i" (by default order="d") and gives the order (decreasing or increasing) the distinct values of X will be sorted.

### Examples

    // first example
    X = [2 8 0 3 7 6 8 7 9 1 6 7 7 2 5 2 2 2 9 7]
    m1 = tabul(X)
    m2 = tabul(X, "i")

    // second example
    X = ["ba" "baba" "a" "A" "AA" "a" "aa" "aa" "aa" "A" "ba"]
    m = tabul(X,"i")

    // third example
    n = 50000;
    X = grand(n,1,"bin",70,0.5);
    m = tabul(X,"i");
    xbasc()
    plot2d3(m(:,1), m(:,2)/n)
    xtitle("empiral probabilities of B(70,0.5)")

    // last example : computes the occurrences of words of the scilab license
    text = read(SCI+"/license.txt",-1,1,"(A)"); // read the scilab license
    bigstr = strcat(text," ");                  // put all the lines in a big string
    sep =  [" " "," "." ";" "*" ":" "-" """"];  // words separators
    words = tokens(bigstr, sep);                // cut the big string into words
    m = tabul(words);                           // computes occurrences of each word
    [occ , p] = sort(m(2));                     // sort by decreasing frequencies
    results = [m(1)(p) string(occ)]             // display result

### See Also

`dsearch` , `histplot` ,

### Authors

  Carlos Klimann (original author)
  J.S. Giet and B. Pincon (new version)

### Bibliography

Wonacott, T.H. & Wonacott, R.J.; Introductory Statistics, fifth edition, J.Wiley & Sons, 1990.