Given that correct assumptions on the baseline survival function are determinant for the validity of further inferences, specific tools to test the fit of a model to real data become essential in proportional hazards models. In this sense, we have proposed a parametric bootstrap to test the fit of survival models. Monte Carlo simulations are used to generate new data sets from the estimates obt...

Nitrous oxide (N(2)O) is a greenhouse gas with a global warming potential approximately 298 times greater than that of CO(2). In 2006, the Intergovernmental Panel on Climate Change (IPCC) estimated N(2)O emission due to synthetic and organic nitrogen (N) fertilization at 1% of applied N. We investigated the uncertainty on this estimated value, by fitting 13 different models to a published datas...

Methods are proposed for estimating real lifetimes and corresponding coefficients from realvalued measurement data in logarithmic scale, where the data are multi-exponential, i.e. represented by linear combinations of decaying exponential functions with various lifetimes. Initial approximations of lifetimes are obtained as peaks of the first derivative of the data, where the first derivative ca...

A FORTRAN IV computer program is presented which fits up to three exponential terms and a constant to experimental data according to a least-squares criterion. Initial estimates are necessary. but no specific kind of spacing is required. The program was tried out on artificially generated three-exponential curves with added white noise. The parameters required could be determined with satisfact...

We propose a new variational EM algorithm for fitting factor analysis models with mixed continuous and categorical observations. The algorithm is based on a simple quadratic bound to the log-sum-exp function. In the special case of fully observed binary data, the bound we propose is significantly faster than previous variational methods. We show that EM is significantly more robust in the prese...

In this paper an exponentially fitted finite difference method is presented for solving singularly perturbed two-point boundary value problems with the boundary layer. A fitting factor is introduced and the model equation is discretized by a finite difference scheme on an uniform mesh. Thomas algorithm is used to solve the tri-diagonal system. The stability of the algorithm is investigated. It ...

There are a couple of purposes in this paper: to study problem approximation with exponential functions and show its relevance for economic science. The solution the first is as conclusive it can be: working max-norm, we determine which datasets have best by means exponentials form f(t)=b+aexp(kt), give necessary sufficient condition some a,b,k∈R be coefficients that approximation, limits when ...