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Lecture 4

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

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Lecture 4

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  1. Lecture 4

  2. 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

  3. 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

  4. 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

  5. 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

  6. Chimps histogram plot(0:5,20*dbinom(0:5,5,.5),type="h",xlab="number of correct answers",ylab="average number of chimps")

  7. 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")

  8. Chimps histogram

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