References

Load packages

library(magrittr)
library(rstan)

Load data

load("../datasets/NorthCarolina_data.dat")
set.seed(201502141)
infantsSample <- infants[sample(x = seq_len(nrow(infants)), size = 100),]

tableone::CreateTableOne(data = infantsSample) %>% print
## NOTE: no factor/logical/character variables supplied, using CreateContTable()
##                     
##                      Overall       
##   n                  100           
##   race (mean (sd))     0.25 (0.44) 
##   sex (mean (sd))      0.53 (0.50) 
##   mage (mean (sd))    27.56 (5.45) 
##   smoker (mean (sd))   0.12 (0.33) 
##   gained (mean (sd))  31.65 (15.18)
##   weight (mean (sd))   3.16 (0.56) 
##   weeks (mean (sd))   38.18 (2.55) 
##   dTime (mean (sd))  999.00 (0.00)
tableone::CreateTableOne(data = infantsSample) %>% print(nonnormal = TRUE)
## NOTE: no factor/logical/character variables supplied, using CreateContTable()
##                        
##                         Overall                
##   n                     100                    
##   race (median [IQR])     0.00 [0.00, 0.25]    
##   sex (median [IQR])      1.00 [0.00, 1.00]    
##   mage (median [IQR])    28.00 [23.00, 31.00]  
##   smoker (median [IQR])   0.00 [0.00, 0.00]    
##   gained (median [IQR])  30.00 [20.00, 40.00]  
##   weight (median [IQR])   3.23 [2.81, 3.60]    
##   weeks (median [IQR])   38.00 [37.00, 40.00]  
##   dTime (median [IQR])  999.00 [999.00, 999.00]
## Population true values
infants$weight %>% mean
## [1] 3.276151
infants$weight %>% var
## [1] 0.3928646
infants$weight %>% sd
## [1] 0.6267891

Create Stan dataset

infants_dat <- list(alpha = 1, beta = 1,
                    N = nrow(infantsSample),
                    y = infantsSample$weight)

Create Stan code string

fileName <- "./Homework_2KY_stan.stan"
stan_code <- readChar(fileName, file.info(fileName)$size)
cat(stan_code)
## data {
##   // Prior alpha
##   int alpha;
##   // Prior beta
##   int beta;  
##   // Define variables in data
##   // Number of observations (an integer)
##   int<lower=0> N;
##   // Birthweight outcome (a real vector of length N)
##   real y[N];
## }
## 
## parameters {
##   // Define parameters to estimate
##   // Population mean (a real number)
##   real mu;
##   // Population variance (a positive real number)
##   real<lower=0> sigmaSq;
## }
## 
## transformed parameters  {
##   // Population standard deviation (a positive real number)
##   real<lower=0> sigma;
##   // Standard deviation (derived from variance)
##   sigma <- sqrt(sigmaSq);
## }
## 
## model {
##   // Prior part of Bayesian inference
##   // Flat prior for mu (no need to specify if non-informative)
##   // sigma^2 has inverse gamma (alpha = 1, beta = 1) prior
##   sigmaSq ~ inv_gamma(alpha, beta);
## 
##   // Likelihood part of Bayesian inference
##   // Outcome model N(mu, sigma^2) (use SD rather than Var)
##   y ~ normal(mu, sigma);    
## }

Run model (Prior alpha = 1, beta = 1)

fit <- stan(model_code = stan_code, data = infants_dat,
            ## file = "./Homework_2KY_stan.stan", # External file method
            iter = 10^4, warmup = 10^3, chains = 3, thin = 10)
## 
## TRANSLATING MODEL 'stan_code' FROM Stan CODE TO C++ CODE NOW.
## COMPILING THE C++ CODE FOR MODEL 'stan_code' NOW.
## In file included from file783117766bf.cpp:8:
## In file included from /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/model/model_header.hpp:17:
## In file included from /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/agrad/rev.hpp:5:
## /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/agrad/rev/chainable.hpp:87:17: warning: 'static' function 'set_zero_all_adjoints' declared in header file should be declared 'static inline' [-Wunneeded-internal-declaration]
##     static void set_zero_all_adjoints() {
##                 ^
## In file included from file783117766bf.cpp:8:
## In file included from /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/model/model_header.hpp:21:
## /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/io/dump.hpp:26:14: warning: function 'product' is not needed and will not be emitted [-Wunneeded-internal-declaration]
##       size_t product(std::vector<size_t> dims) {
##              ^
## 2 warnings generated.
## 
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## 
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## 
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## Show model results
fit
## Inference for Stan model: stan_code.
## 3 chains, each with iter=10000; warmup=1000; thin=10; 
## post-warmup draws per chain=900, total post-warmup draws=2700.
## 
##         mean se_mean   sd 2.5%  25%  50%  75% 97.5% n_eff Rhat
## mu      3.16    0.00 0.06 3.05 3.12 3.16 3.20  3.28  2562    1
## sigmaSq 0.33    0.00 0.05 0.25 0.29 0.33 0.36  0.43  2700    1
## sigma   0.57    0.00 0.04 0.50 0.54 0.57 0.60  0.66  2700    1
## lp__    5.93    0.02 1.04 3.12 5.56 6.24 6.67  6.94  2700    1
## 
## Samples were drawn using NUTS(diag_e) at Mon Feb 23 12:56:37 2015.
## For each parameter, n_eff is a crude measure of effective sample size,
## and Rhat is the potential scale reduction factor on split chains (at 
## convergence, Rhat=1).
plot(fit)

traceplot(fit, inc_warmup = FALSE)

## Extract data
s <- rstan::extract(fit, inc_warmup = FALSE)
summary(s$mu)
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##   2.964   3.121   3.161   3.161   3.201   3.389
summary(s$sigmaSq)
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##  0.2099  0.2947  0.3255  0.3295  0.3587  0.5292
infants_dat$alpha <- 2; infants_dat$beta <- 1
fit2 <- stan(model_code = stan_code, data = infants_dat,
             iter = 10^4, warmup = 10^3, chains = 3, thin = 10)
## 
## TRANSLATING MODEL 'stan_code' FROM Stan CODE TO C++ CODE NOW.
## COMPILING THE C++ CODE FOR MODEL 'stan_code' NOW.
## In file included from file78354a52851.cpp:8:
## In file included from /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/model/model_header.hpp:17:
## In file included from /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/agrad/rev.hpp:5:
## /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/agrad/rev/chainable.hpp:87:17: warning: 'static' function 'set_zero_all_adjoints' declared in header file should be declared 'static inline' [-Wunneeded-internal-declaration]
##     static void set_zero_all_adjoints() {
##                 ^
## In file included from file78354a52851.cpp:8:
## In file included from /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/model/model_header.hpp:21:
## /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/io/dump.hpp:26:14: warning: function 'product' is not needed and will not be emitted [-Wunneeded-internal-declaration]
##       size_t product(std::vector<size_t> dims) {
##              ^
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## 
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fit2
## Inference for Stan model: stan_code.
## 3 chains, each with iter=10000; warmup=1000; thin=10; 
## post-warmup draws per chain=900, total post-warmup draws=2700.
## 
##         mean se_mean   sd 2.5%  25%  50%  75% 97.5% n_eff Rhat
## mu      3.16    0.00 0.05 3.05 3.12 3.16 3.20  3.27  2675    1
## sigmaSq 0.32    0.00 0.04 0.25 0.29 0.32 0.35  0.42  2669    1
## sigma   0.57    0.00 0.04 0.50 0.54 0.57 0.59  0.65  2661    1
## lp__    7.17    0.02 0.94 4.73 6.79 7.46 7.84  8.09  2700    1
## 
## Samples were drawn using NUTS(diag_e) at Mon Feb 23 12:57:11 2015.
## For each parameter, n_eff is a crude measure of effective sample size,
## and Rhat is the potential scale reduction factor on split chains (at 
## convergence, Rhat=1).
infants_dat$alpha <- 2; infants_dat$beta <- 2
fit3 <- stan(model_code = stan_code, data = infants_dat,
             iter = 10^4, warmup = 10^3, chains = 3, thin = 10)
## 
## TRANSLATING MODEL 'stan_code' FROM Stan CODE TO C++ CODE NOW.
## COMPILING THE C++ CODE FOR MODEL 'stan_code' NOW.
## In file included from file78369759e64.cpp:8:
## In file included from /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/model/model_header.hpp:17:
## In file included from /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/agrad/rev.hpp:5:
## /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/agrad/rev/chainable.hpp:87:17: warning: 'static' function 'set_zero_all_adjoints' declared in header file should be declared 'static inline' [-Wunneeded-internal-declaration]
##     static void set_zero_all_adjoints() {
##                 ^
## In file included from file78369759e64.cpp:8:
## In file included from /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/model/model_header.hpp:21:
## /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/io/dump.hpp:26:14: warning: function 'product' is not needed and will not be emitted [-Wunneeded-internal-declaration]
##       size_t product(std::vector<size_t> dims) {
##              ^
## 2 warnings generated.
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fit3
## Inference for Stan model: stan_code.
## 3 chains, each with iter=10000; warmup=1000; thin=10; 
## post-warmup draws per chain=900, total post-warmup draws=2700.
## 
##         mean se_mean   sd 2.5%  25%  50%  75% 97.5% n_eff Rhat
## mu      3.16    0.00 0.06 3.05 3.12 3.16 3.20  3.28  2470    1
## sigmaSq 0.34    0.00 0.05 0.26 0.31 0.34 0.37  0.45  2177    1
## sigma   0.58    0.00 0.04 0.51 0.56 0.58 0.61  0.67  2194    1
## lp__    4.04    0.02 1.01 1.36 3.66 4.34 4.76  5.01  2543    1
## 
## Samples were drawn using NUTS(diag_e) at Mon Feb 23 12:57:44 2015.
## For each parameter, n_eff is a crude measure of effective sample size,
## and Rhat is the potential scale reduction factor on split chains (at 
## convergence, Rhat=1).
infants_dat$alpha <- 2; infants_dat$beta <- 5
fit4 <- stan(model_code = stan_code, data = infants_dat,
             iter = 10^4, warmup = 10^3, chains = 3, thin = 10)
## 
## TRANSLATING MODEL 'stan_code' FROM Stan CODE TO C++ CODE NOW.
## COMPILING THE C++ CODE FOR MODEL 'stan_code' NOW.
## In file included from file7832313f925.cpp:8:
## In file included from /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/model/model_header.hpp:17:
## In file included from /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/agrad/rev.hpp:5:
## /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/agrad/rev/chainable.hpp:87:17: warning: 'static' function 'set_zero_all_adjoints' declared in header file should be declared 'static inline' [-Wunneeded-internal-declaration]
##     static void set_zero_all_adjoints() {
##                 ^
## In file included from file7832313f925.cpp:8:
## In file included from /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/model/model_header.hpp:21:
## /Library/Frameworks/R.framework/Versions/3.1/Resources/library/rstan/include//stansrc/stan/io/dump.hpp:26:14: warning: function 'product' is not needed and will not be emitted [-Wunneeded-internal-declaration]
##       size_t product(std::vector<size_t> dims) {
##              ^
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## 
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fit4
## Inference for Stan model: stan_code.
## 3 chains, each with iter=10000; warmup=1000; thin=10; 
## post-warmup draws per chain=900, total post-warmup draws=2700.
## 
##          mean se_mean   sd  2.5%   25%   50%   75% 97.5% n_eff Rhat
## mu       3.16    0.00 0.06  3.04  3.12  3.16  3.20  3.28  2637    1
## sigmaSq  0.40    0.00 0.06  0.31  0.36  0.40  0.44  0.52  2700    1
## sigma    0.63    0.00 0.04  0.56  0.60  0.63  0.66  0.72  2700    1
## lp__    -4.23    0.02 0.95 -6.66 -4.59 -3.95 -3.56 -3.28  2409    1
## 
## Samples were drawn using NUTS(diag_e) at Mon Feb 23 12:58:15 2015.
## For each parameter, n_eff is a crude measure of effective sample size,
## and Rhat is the potential scale reduction factor on split chains (at 
## convergence, Rhat=1).