Description Usage Arguments Value See Also Examples
Fits exponential beta curves to 13C breath test series data using Bayesian Stan methods. See https://mennebiomed.de/blog/breathteststan for a comparision between single curve, mixedmodel population and Bayesian methods.
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data 
Data frame or tibble as created by 
dose 
Dose of acetate or octanoate. Currently, only one common dose for all records is supported. 
sample_minutes 
If mean sampling interval is < sampleMinutes, data are subsampled using a spline algorithm 
student_t_df 
When student_t_df < 10, the student distribution is used to model the residuals. Recommended values to model typical outliers are from 3 to 6. When student_t_df >= 10, the normal distribution is used. 
chains 
Number of chains for Stan 
iter 
Number of iterations for each Stan chain 
model 
Name of model; use 
seed 
Optional seed for rstan 
A list of classes "breathteststanfit" and "breathtestfit" with elements
coef
Estimated parameters as data frame in a keyvalue format with
columns patient_id, group, parameter, method
and value
.
Has an attribute AIC.
data
The effectively analyzed data. If density of points
is too high, e.g. with BreathId devices, data are subsampled before fitting.
stan_fit
The Stan fit for use with shinystan::launch_shiny
or extraction of chains.
Base methods coef, plot, print
; methods from package
broom: tidy, augment
.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30  library(breathtestcore)
suppressPackageStartupMessages(library(dplyr))
d = breathtestcore::simulate_breathtest_data(n_records = 3) # default 3 records
data = breathtestcore::cleanup_data(d$data)
# Use more than 80 iterations and 4 chains for serious fits
fit = stan_fit(data, chains = 1, iter = 80)
plot(fit) # calls plot.breathtestfit
# Extract coefficients and compare these with those
# used to generate the data
options(digits = 2)
cf = coef(fit)
cf %>%
filter(grepl("mkbeta", parameter )) %>%
select(method, group) %>%
tidyr::spread(parameter, value) %>%
inner_join(d$record, by = "patient_id") %>%
select(patient_id, m_in = m.y, m_out = m.x,
beta_in = beta.y, beta_out = beta.x,
k_in = k.y, k_out = k.x)
# For a detailed analysis of the fit, use the shinystan library
library(shinystan)
# launch_shinystan(fit$stan_fit)
# The following plots are somewhat degenerate because
# of the few iterations in stan_fit
suppressPackageStartupMessages(library(rstan))
stan_plot(fit$stan_fit, pars = c("beta[1]","beta[2]","beta[3]"))
stan_plot(fit$stan_fit, pars = c("k[1]","k[2]","k[3]"))
stan_plot(fit$stan_fit, pars = c("m[1]","m[2]","m[3]"))

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