The caterpillar plot is a side-by-side bar plot of 95% intervals for multiple parameters. Typically, it is used to visualize and compare random-effects parameters, which can come in large numbers in certain models. You can use the %CATER autocall macro to create a caterpillar plot. The %CATER macro requires you specify an input data set and a list of variables that you want to plot.
A random-effects model that has 21 random-effects parameters is used here for illustrational purpose. For an explanation of the random-effects model and the data involved, see Logistic Regression Random-Effects Model. The following statements generate a SAS data set and fit the model:
title 'Create a Caterpillar Plot'; data seeds; input r n seed extract @@; ind = _N_; datalines; 10 39 0 0 23 62 0 0 23 81 0 0 26 51 0 0 17 39 0 0 5 6 0 1 53 74 0 1 55 72 0 1 32 51 0 1 46 79 0 1 10 13 0 1 8 16 1 0 10 30 1 0 8 28 1 0 23 45 1 0 0 4 1 0 3 12 1 1 22 41 1 1 15 30 1 1 32 51 1 1 3 7 1 1 ;
ods select none; proc mcmc data=seeds outpost=postout seed=332786 nmc=20000; parms beta0 0 beta1 0 beta2 0 beta3 0 s2 1; prior s2 ~ igamma(0.01, s=0.01); prior beta: ~ general(0); w = beta0 + beta1*seed + beta2*extract + beta3*seed*extract; random delta ~ normal(w, var=s2) subject=ind; pi = logistic(delta); model r ~ binomial(n = n, p = pi); run; ods select all;
The output data set Postout
contains posterior draws for all 21 random-effects parameters, delta_1
delta_21
. You can use the following statements to generate a caterpillar plot for the 21 parameters:
ods graphics on; %CATER(data=postout, var=delta:); ods graphics off;
Figure 61.17 is a caterpillar plot of the random-effects parameters delta_1
–delta_21
.
If you want to change the display of the caterpillar plot, such as using a different line pattern, color, or size of the markers,
you need to first modify the Stat.MCMC.Graphics.Caterpillar
template and then call the %CATER macro again.
You can use the following statements to view the source of the Stat.MCMC.Graphics.Caterpillar
template:
proc template; path sashelp.tmplmst; source Stat.MCMC.Graphics.Caterpillar; run;
Figure 61.18 lists the source statements of the template that is used to generate the template for the caterpillar plot.
Figure 61.18: Source Statements for Stat.MCMC.Graphics.Caterpillar Template
define statgraph Stat.MCMC.Graphics.Caterpillar; dynamic _OverallMean _VarName _VarMean _XLower _XUpper _byline_ _bytitle_ _byfootnote_; begingraph; entrytitle "Caterpillar Plot"; layout overlay / yaxisopts=(offsetmin=0.05 offsetmax=0.05 display=(line ticks tickvalues)) xaxisopts=(display=(line ticks tickvalues)); referenceline x=_OVERALLMEAN / lineattrs=(color= GraphReference:ContrastColor); HighLowPlot y=_VARNAME high=_XUPPER low=_XLOWER / lineattrs= GRAPHCONFIDENCE; scatterplot y=_VARNAME x=_VARMEAN / markerattrs=(size=5 symbol= circlefilled); endlayout; if (_BYTITLE_) entrytitle _BYLINE_ / textattrs=GRAPHVALUETEXT; else if (_BYFOOTNOTE_) entryfootnote halign=left _BYLINE_; endif; endif; endgraph; end; |
You can use the TEMPLATE procedure (see Chapter 21: Statistical Graphics Using ODS) to run any modified SAS/GRAPH graph template definition and then call the %CATER macro again. The %CATER macro picks up the change you made to the Caterpillar template and displays the new graph accordingly.