###################################################################### ### R for College Mathematics and Statistics ### Thomas J Pfaff ### Code for Appendix A: Loops, Vectors, and Apply ###################################################################### total=0 for (i in 1:100){ total=total+ 1/i^2 } total f=function(x){1/x^2} sum(f(1:100)) sum(sapply(1:100,function(x){1/x^2})) vector1=numeric(100) vector1[1]=1 for (i in 2:100){ vector1[i]=vector1[i-1]+ 1/i^2} vector1[c(1:3,98:100)] f=function(x){1/x^2} vector2=cumsum(f(1:100)) vector2[c(1:3,98:100)] vector3=cumsum(sapply(1:100,function(x){1/x^2})) vector3[c(1:3,98:100)] set.seed(42) A=matrix(sample(1:10,50,replace=TRUE), ncol=10) A ## Book error: There is a missing + between count1[col.j] and ifelse(). count1=numeric(10) for(col.j in 1:10){ for(row.i in 1:5) { count1[col.j]=count1[col.j]+ ifelse(A[row.i,col.j]%%2==0,1,0)}} count1 count2=apply(A,2,function(x){sum(ifelse(x%%2==0,1,0))}) count2