Caterpillar Plot with PROC MCMC

The script first generates a 'seeds' dataset containing germination results. It then uses the `PROC MCMC` procedure to fit a binomial model with a logit link function and random effects ('delta'). The posterior distribution samples are saved in the 'postout' table. A `%CATER` macro is called to create the Caterpillar plot of the random effects. Finally, a `PROC TEMPLATE` step is used to view the source of the associated graph template.

Data Analysis

Type : CREATION_INTERNE

The data used ('seeds') is created directly in the script via a DATA step using the DATALINES statement.

1 Code Block

DATA STEP Data

Explanation :
Creates the 'seeds' dataset containing variables r, n, seed, extract and an observation identifier 'ind'. The data is included directly in the code.

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1	DATA seeds;
2	INPUT r n seed extract;
3	ind = _N_;
4	DATALINES;
5	10 39 0 0 23 62 0 0 23 81 0 0 26 51 0 0
6	17 39 0 0 5 6 0 1 53 74 0 1 55 72 0 1
7	32 51 0 1 46 79 0 1 10 13 0 1 8 16 1 0
8	10 30 1 0 8 28 1 0 23 45 1 0 0 4 1 0
9	3 12 1 1 22 41 1 1 15 30 1 1 32 51 1 1
10	3 7 1 1
11	;

2 Code Block

PROC MCMC Data

Explanation :
Performs a Bayesian (MCMC) analysis on the 'seeds' data. Defines a binomial logistic model with random effects 'delta'. Posterior samples are stored in 'postout'. Result display is temporarily disabled to optimize execution.

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1	ods select none;
2	PROC MCMC DATA=seeds outpost=postout seed=332786 nmc=20000;
3	parms beta0 0 beta1 0 beta2 0 beta3 0 s2 1;
4	prior s2 ~ igamma(0.01, s=0.01);
5	prior beta: ~ general(0);
6	w = beta0 + beta1seed + beta2extract + beta3seedextract;
7	random delta ~ normal(w, var=s2) subject=ind;
8	pi = logistic(delta);
9	model r ~ binomial(n = n, p = pi);
10	RUN;
11	ods select all;

3 Code Block

Macro Call

Explanation :
Calls the `%CATER` macro (assumed to be defined in the environment or an autocall library) to generate the Caterpillar plot of variables starting with 'delta' from the 'postout' dataset.

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1	%CATER(DATA=postout, var=delta:);

4 Code Block

PROC TEMPLATE

Explanation :
Displays the source code of the ODS graph template 'Stat.MCMC.Graphics.Caterpillar' stored in 'sashelp.tmplmst', allowing inspection of the graph definition used.

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1	PROC TEMPLATE;
2	path sashelp.tmplmst;
3	SOURCE Stat.MCMC.Graphics.Caterpillar;
4	RUN;

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