Blog Archives

Long-term precipitation data for your location from the US Historical Climatology Network using R

September 19, 2012
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Long-term precipitation data for your location from the US Historical Climatology Network using R

Abstract Long-term daily precipitation records from the US Historical Climatology Network (USHCN) are processed and summarized using R. Below is R code which examines the data from Livermore, CA, the closest available USHCN station to my present home ...

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California High School Graduation and Dropout Rates

September 16, 2012
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California High School Graduation and Dropout Rates

Abstract The California Deparment of Education recently (June 2012) had a news release on the increase in high school (grades 9-12) graduation rates and decrease in dropout rates. The data used by the Department was from two cohorts (4-year periods) o...

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Fixing non positive definite correlation matrices using R

September 3, 2012
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Problem When a correlation or covariance matrix is not positive definite (i.e., in instances when some or all eigenvalues are negative), a cholesky decomposition cannot be performed. Sometimes, these eigenvalues are very small negative numbers and occ...

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