This function computes the probability density of the Singh--Maddala (Burr Type XII) distribution given parameters (\(a\), \(b\), and \(q\)) computed by parsmd
. The probability density function is
$$f(x) = \frac{b \cdot q \cdot x^{b-1}}{a^b \biggl(1 + \bigl[(x-\xi)/a\bigr]^b \biggr)^{q+1}}\mbox{,}$$
where \(f(x)\) is the probability density for quantile \(x\) with \(0 \le x \le \infty\), \(\xi\) is a location parameter, \(a\) is a scale parameter (\(a > 0\)), \(b\) is a shape parameter (\(b > 0\)), and \(q\) is another shape parameter (\(q > 0\)).
pdfsmd(x, para)
Probability density (\(f\)) for \(x\).
A real value vector.
The parameters from parsmd
or vec2par
.
W.H. Asquith
Kumar, D., 2017, The Singh--Maddala distribution---Properties and estimation: International Journal of System Assurance Engineering and Management, v. 8, no. S2, 15 p., tools:::Rd_expr_doi("10.1007/s13198-017-0600-1").
Shahzad, M.N., and Zahid, A., 2013, Parameter estimation of Singh Maddala distribution by moments: International Journal of Advanced Statistics and Probability, v. 1, no. 3, pp. 121--131, tools:::Rd_expr_doi("10.14419/ijasp.v1i3.1206").
cdfsmd
, quasmd
, lmomsmd
, parsmd