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See the recommended documentation of this function
samplef
sample values with replacement from a population with given frequencies.
Calling Sequence
s = samplef(n,X,f,orient)
Arguments
- n
positive integer (size of sample)
- X
matrix. Population, samples are extracted from this matrix
- f
matrix of positive real values. Indicates the corresponding frequencies of the values in
X
.- orient
Optional parameter. Admissible values are
{'*'}, 1, 2, 'r'
or'c'
. The orientation to sample rows or columns. See Description below.- s
vector or matrix containing the sampled values of
X
at frequenciesf
.
Description
This function returns s
, a vector of length n
. It contains
a sample of n
extractions, with replacement, from the
vector (or matrix) X
, each element counted with the
frequency given by the corresponding value in vector f
.
s=samplef(n,X,f)
(or
s=samplef(n,X,f,'*')
) returns a
vector s
whose values are a random sample of n values from
X
, each value with a probability to be sampled
proportional to the corresponding value of f
, extracted
with replacement, from X
. f
must have same length than X
.
s=samplef(n,X,f,'r')
(or, equivalently,
s=samplef(n,X,f,1))
returns a matrix of type
size(X,'r') * n
. It contains a random sample of n
rows from
X
, each row with a probability to be sampled proportional
to the corresponding value of f
, extracted with
replacement, from the rows of X
. The length of f
must be
equal to the number of rows of X
.
s=samplef(n,X,f,'c')
(or, equivalently,
s=samplef(n,X,f,2))
returns a matrix of type
n * size(X,'c')
. It contains a random sample of n
columns
from X
, each column with a probability to be sampled
proportional to the corresponding value of f
, extracted
with replacement, from the columns of X
. The length of f
must be equal to the number of columns of X
.
Random number generator
samplef
is based on grand for generating the random samples. Use grand("setsd", seed)
to change the seed for samplef
.
Examples
X = [3 7 9; 22 4 2]; f1 = [10 1 1 1 1 1]; f2 = [1 ; 15]; f3 = [10 1 1]; s=samplef(20, X, f1) //the first value of matrix X will be choosen with frequency 10/15 s=samplef(20, X, f2, 'r') //the second row of matrix a will be choosen with frequency 15/16 s=samplef(20, X, f3, 'c') //the first column of matrix a will be choosen with frequency 10/12
See Also
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