Error In Chol.default
Tour Start here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Cross Validated Questions Tags Users Badges Unanswered Ask Question _ Cross Validated is a question and answer site for people interested in statistics, machine learning, data analysis, data mining, and data visualization. Join them; it only takes a minute: Sign up Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top R Error in chol.default(A) krigeST from gstat package up vote 1 down vote favorite 1 I am working with an hourly dataset of air temperature, recorded at ~200 stations over a relatively small area. I chose a space-time variogram (e.g. sum-metric) to fit my data and am now trying to make predictions over my same stations in order to fill NA (missing value) gaps. When using the krigeST() function over daily aggregated data everything seems to go smooth but when I use it at the original hourly resolution I always get the following error: Error in chol.default(A) the leading minor of order 68 is not positive definite I googled it and found that it is related to a matrix not being completely positive-definite. However, I am not sure why this happens and was wondering if any of you know a way of fixing this (a workaround to avoid it). Thanks! In the empirical semivariogram model I specify initial values for the nugget and all other parameters. Then the optimal value is found by using the fit.variogram() function, which returns a value of 0 for the spatial, temporal, and joint spatio-temporal nugget. Do you think the problem comes from here? Why would a nugget of 0 cause that? In general I am not trying to predict over a spatial grid, rather I am trying to predict on the same observations I use to develop the variogram.
[ date ] [ thread ] [ subject ] [ author ] see inline! On Mon, Jun 18, 2012 at 12:38 AM,
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of http://stackoverflow.com/questions/25063157/r-error-in-chol-defaulta-krigest-from-gstat-package this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up error in R Error in chol.default(A) krigeST from gstat package up vote 0 down vote favorite I am working with an hourly dataset of air temperature, recorded at ~200 stations over a relatively small area. I chose a space-time variogram (e.g. sum-metric) to fit my data and am now trying to make predictions over my same stations in order to fill NA (missing value) gaps. When error in chol.default using the krigeST() function over daily aggregated data everything seems to go smooth but when I use it at the original hourly resolution I always get the following error: Error in chol.default(A) the leading minor of order 68 is not positive definite I googled it and found that it is related to a matrix not being completely positive-definite. However, I am not sure why this happens and was wondering if any of you know a way of fixing this (a workaround to avoid it). r kriging gstat covariogram share|improve this question edited Dec 4 '15 at 16:01 Tim B 28.7k94688 asked Jul 31 '14 at 15:36 user20038 184 add a comment| 1 Answer 1 active oldest votes up vote 0 down vote There are several possibilities that lead to a singular covariance matrix. Two common ones: duplicate observations (identical location & time stamp), a variogram model that does not discriminate observations sufficiently, leading to near-perfectly correlated observations. share|improve this answer answered Jan 18 '15 at 23:19 Edzer Pebesma 1,703512 add a comment| Your Answer draft saved draft discarded Sign up or log in Sign up using Go