If you are experiencing problems downloading PDF or HTML fulltext, our helpdesk recommend clearing your browser cache and trying again. If you need help in clearing your cache, please click here . Still need help? Email help@ingentaconnect.com

Fitting Discrete-Time Dynamic Models Having Any Time Interval

$29.50 plus tax (Refund Policy)

Buy Article:


When the desired time interval of a difference equation is not the same as the interval at which the data used to fit the equation were collected (the measurement interval), some kind of interpolation method is necessary before fitting. Linear growth assumptions, which are often used for such interpolations, are almost always inconsistent with the growth function that is estimated and can lead to biased growth projections. A more logical approach is to use the hypothesized functional form of the difference equation as the basis for interpolation. Two interpolation methods based on this approach are presented. With one method, both the interpolation and the parameter estimation steps are implemented simultaneously. The second method implements the interpolation and parameter estimation steps separately and requires repeated model fittings until consistency is obtained between both steps. The procedures are demonstrated using a tree height growth example. Results are compared with an integrated, continuous-time version of the growth model that can be fitted without interpolation. Growth projections obtained with the proposed interpolation methods are closer to the projections obtained with the integrated, continuous-time model than projections obtained with other commonly used interpolation methods. A simple Monte Carlo analysis showed that two common interpolation methods based on linear assumptions produce biased parameter estimates but failed to show any bias in the parameter estimates obtained with the proposed methods. Parameter estimates obtained with the new interpolation methods converge to limiting values as the time interval of the difference equation is shortened. These limiting values can be used as estimates of the parameters of continuous-time versions of the growth model. For. Sci. 39(3):499-519.

Keywords: Growth equations; difference equations; interpolation

Document Type: Journal Article

Affiliations: Senior Research Associate, Dept. of Forestry, Virginia Tech, Blacksburg, VA 24061

Publication date: August 1, 1993

More about this publication?
  • Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.
  • Membership Information
  • ingentaconnect is not responsible for the content or availability of external websites
Related content



Share Content

Access Key

Free Content
Free content
New Content
New content
Open Access Content
Open access content
Subscribed Content
Subscribed content
Free Trial Content
Free trial content
Cookie Policy
Cookie Policy
ingentaconnect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more