Volume 12 - Article 5 | Pages 105–106  

Quadratic spline fits by nonlinear least squares

By Carl Schmertmann

Abstract

This web program fits a Quadratic Spline model, as described in Schmertmann (2003; Demographic Research Volume 9, Article 5), to any empirical fertility schedule supplied by the user. The fit minimizes the sum of squared differences between the empirical nfx values and the nfx values from the QS model schedule. Output includes parameter estimates, a graphical depiction of the fitted schedule, and several text reports. Users do not need specialized statistical software or a particular operating system to run the program; the only requirement is a web browser.

Software
http://www.demographic-research.org/Volumes/Vol12/5/qsfit/qsfit.html

Author’s Affiliation

• Carl Schmertmann - Florida State University, United States of America EMAIL

Other articles by the same author/authors in Demographic Research

Data errors in mortality estimation: Formal demographic analysis of under-registration, under-enumeration, and age misreporting
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D-splines: Estimating rate schedules using high-dimensional splines with empirical demographic penalties
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Revivorship and life lost to mortality
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Editorial: The past, present, and future of Demographic Research
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Stationary populations with below-replacement fertility
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A system of model fertility schedules with graphically intuitive parameters
Volume 9 - Article 5

Estimating Parametric Fertility Models with Open Birth Interval Data
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