Multiple indexing with Stan
January 15, 2020, 8:00 pmSummary
Using vectors for indexed access to ragged arrays in Stan
volume ~ normal(
v0[record] .* (1+ kappa[record] .* (minute ./ tempt[record])) .*
exp(-minute ./ tempt[record]), sigma);Fitting gastric emptying time series
Gastric volume times serie measured by MRI techniques can have an initial volume overshoot due to secretion. To estimate half-times and the degree of overshoot, the author of this blog has introduced the linexp function [@Fruehauf2011] with three parameters to complement the power exponential function used in earlier research [@Elashoff1982, @Elashoff1983b] with scintigraphic data.
linexp:
v = v0* (1+t*kappa/tempt)*exp(-t/t_{empt})13C Breath test: Population Fit and Bayesian Models
January 15, 2020, 7:10 pm
Summary
Time series from 13C breath test recordings are used as a surrogate indicator for gastric emptying. Gastric emptying half time t50 is computed by fitting the series with an exponential beta or a Gamma function. Often, records are too short to obtain stable estimates of the trailing par...