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Lecture 4 Runs • Q: – Toss a coin 1000000 times. – Run is an unbroken sequence of H in a row – What is the length of the longest run • Take guesses (closest will get a cookie) • We will write an R code togather Issues • Case sensitive dog and Dog are different • Careful of extra spaces • Brackets –() • arguments of functions sum(coin); for(i in 1:10), if(coin<1) • grouping math formulas (1+3)*(4+5) – [ ] indexing valus in a list coin[10] – { } grouping commands togather Are we smarter than chimps? • In each of the following pair one country has twice the child mortality rate than the other. – Malaysia or Russia – Poland or South Korea – Pakistan or Vietnam – Thailand or South Africa – Sri Lanka or Turkey Answers • In each of the following pair one country has twice the child mortality rate than the other. – Malaysia or Russia – Poland or South Korea – Pakistan or Vietnam – Thailand or South Africa – Sri Lanka or Turkey • Collect data and draw a histogram Chimps histogram plot(0:5,20*dbinom(0:5,5,.5),type="h",xlab="number of correct answers",ylab="average number of chimps") What about uncertainty • 1000 classes of chimps simulated. – Classes ordered based on average performance – Will Show: Worst class, 2.5%, 5%, 25% nclass=1000 nchimps=20 nquestions=5 count1=matrix(0,nrow=nclass,ncol=nquestions+1) m1=rep(0,nclass) for (i in 1:nclass){ data1=rbinom(nchimps,nquestions,.5) count1[i,]=tabulate(data1,nquestions+1) m1[i]=mean(data1) } i1=order(m1) i2=order(count1[,1]) par(mfrow=c(2,2)) plot(0:5,count1[i1[1],],type="h",xlab="number of correct answers",ylab="average number of chimps",sub="1:1000") plot(0:5,count1[i1[25],],type="h",xlab="number of correct answers",ylab="average number of chimps",sub="25:1000") plot(0:5,count1[i1[50],],type="h",xlab="number of correct answers",ylab="average number of chimps",sub="50:1000") plot(0:5,count1[i1[250],],type="h",xlab="number of correct answers",ylab="average number of chimps",sub="250:1000") Chimps histogram