nag_rand_gen_discrete (g05tdc) generates a sequence of
integers
, from a discrete distribution defined by information supplied in
p. This may either be the PDF or CDF of the distribution. A reference vector is first set up to contain the CDF of the distribution in its higher elements, followed by an index.
Setting up the reference vector and subsequent generation of variates can each be performed by separate calls to nag_rand_gen_discrete (g05tdc) or may be combined in a single call.
One of the initialization functions
nag_rand_init_repeatable (g05kfc) (for a repeatable sequence if computed sequentially) or
nag_rand_init_nonrepeatable (g05kgc) (for a non-repeatable sequence) must be called prior to the first call to
nag_rand_gen_discrete (g05tdc).
- 1:
– Nag_ModeRNGInput
-
On entry: a code for selecting the operation to be performed by the function.
- Set up reference vector only.
- Generate variates using reference vector set up in a prior call to nag_rand_gen_discrete (g05tdc).
- Set up reference vector and generate variates.
- Generate variates without using the reference vector.
Constraint:
, , or .
- 2:
– IntegerInput
-
On entry: , the number of pseudorandom numbers to be generated.
Constraint:
.
- 3:
– const doubleInput
-
On entry: the PDF or CDF of the distribution.
Constraints:
- , for ;
- if , ;
- if , .
- 4:
– IntegerInput
-
On entry: the number of values supplied in
p defining the PDF or CDF of the discrete distribution.
Constraint:
.
- 5:
– IntegerInput
-
On entry: the value of the variate, a whole number, to which the probability in corresponds.
- 6:
– Nag_DiscreteDistribInput
-
On entry: indicates the type of information contained in
p.
- p contains a probability distribution function (PDF).
- p contains a cumulative distribution function (CDF).
Constraint:
or .
- 7:
– doubleCommunication Array
-
On entry: if , the reference vector from the previous call to nag_rand_gen_discrete (g05tdc).
On exit: the reference vector.
- 8:
– IntegerInput
-
On entry: the dimension of the array
r.
Suggested values:
- if , approximately (for optimum efficiency in generating variates);
- otherwise .
Constraints:
- if or , ;
- if , lr should remain unchanged from the previous call to nag_rand_gen_discrete (g05tdc).
- 9:
– IntegerCommunication Array
-
Note: the dimension,
, of this array is dictated by the requirements of associated functions that must have been previously called. This array MUST be the same array passed as argument
state in the previous call to
nag_rand_init_repeatable (g05kfc) or
nag_rand_init_nonrepeatable (g05kgc).
On entry: contains information on the selected base generator and its current state.
On exit: contains updated information on the state of the generator.
- 10:
– IntegerOutput
-
On exit: contains pseudorandom numbers from the specified discrete distribution.
- 11:
– NagError *Input/Output
-
The NAG error argument (see
Section 3.7 in How to Use the NAG Library and its Documentation).
Not applicable.
Please consult the
x06 Chapter Introduction for information on how to control and interrogate the OpenMP environment used within this function. Please also consult the
Users' Note for your implementation for any additional implementation-specific information.
None.
This example prints
pseudorandom variates from a discrete distribution whose PDF,
, is defined as follows:
The reference vector is set up and and the variates are generated by a single call to
nag_rand_gen_discrete (g05tdc), after initialization by
nag_rand_init_repeatable (g05kfc).
None.