x<-rnorm(1000)

x

y<-matrix(x,10,100)

y

vv<-rep(NA,100)

vv

for(i in 1:100){

vv[i]<-var(y[ ,i])

i=i+1

}

vv

yy<-matrix(vv,100,1)

yy

s=0

for(i in 1:100){

for(k in i:100){

if (yy[i,1] > yy[k,1]){

s=s+1}

else{s=s

}

k=k+1

}

i=i+1

}

s

> set.seed(123)

> rnorm(4)

[1] -0.56047565 -0.23017749  1.55870831  0.07050839

> rnorm(4)

[1]  0.1292877  1.7150650  0.4609162 -1.2650612

> set.seed(123)

> rnorm(4)

[1] -0.56047565 -0.23017749  1.55870831  0.07050839

> sample(1:6, 10, replace=TRUE)

 [1] 2 2 5 3 5 3 5 6 3 5

> set.seed(1)

> sample(1:6, 10, replace=TRUE)

 [1] 2 3 4 6 2 6 6 4 4 1

> sample(1:6, 10, replace=TRUE)

 [1] 2 2 5 3 5 3 5 6 3 5

> set.seed(1)

> sample(1:6, 10, replace=TRUE)

 [1] 2 3 4 6 2 6 6 4 4 1

> set.seed(123)

> index <- sample(1:nrow(iris), 5)

> index

[1] 44 119 62 133 142

> iris[index, ]

  Sepal.Length Sepal.Width Petal.Length Petal.Width  Species

44      5.0     3.5     1.6     0.6   setosa

119     7.7     2.6     6.9     2.3 virginica

62      5.9     3.0     4.2     1.5 versicolor

133     6.4     2.8     5.6     2.2 virginica

142     6.9     3.1     5.1     2.3 virginica

R> sample(LETTERS, 5)
[1] "K" "N" "R" "Z" "G"
R> sample(LETTERS, 5)
[1] "L" "P" "J" "E" "D"
R> set.seed(42); sample(LETTERS, 5)
[1] "X" "Z" "G" "T" "O"
R> set.seed(42); sample(LETTERS, 5)
[1] "X" "Z" "G" "T" "O"

mytrans <- function(x) {
  if (!is.matrix(x)) {
    warning("argument is not a matrix: returning NA")
    return(NA_real_)
  }
  y <- matrix(1, nrow=ncol(x), ncol=nrow(x))
  for (i in 1:nrow(x)) {
    for (j in 1:ncol(x)) {
      y[j,i] <- x[i,j]
    }
  }
return(y)
}

# try it
z <- matrix(1:10, nrow=5, ncol=2)
z
tz <- mytrans(z)
tz

#install.packages("rngWELL")

#install.packages("randtoolbox")

library(rngWELL)

library(randtoolbox)

halt=halton(10,dim=1)

halt

write.csv(halt,"halt.csv")

> pmin(c(1,4,9),c(2,3,10))
[1] 1 3 9

> x=1:10
> cumsum(x)
 [1]  1  3  6 10 15 21 28 36 45 55
> 

> x=1:10
> cumprod(x)
 [1]       1       2       6      24     120     720    5040   40320  362880
[10] 3628800
> 

> round(sqrt(2),4)
[1] 1.4142

expression

> D(expression(sinx+cosy),"y")

[1] 0

> D(expression(sin(x)+cos(y)),"y")

-sin(y)

> D(expression(log(sin(y)),"y")

+ D(expression(log(sin(y)),"y")

Error: unexpected symbol in:

"D(expression(log(sin(y)),"y")

D"

> D(expression(log(sin(y))),"y")

cos(y)/sin(y)

> 

library(animation)

ani.options(nmax = 20)

par(mar = c(1, 1, 1, 1))

vi.lilac.chaser()

set.seed(20111105)
x = rbind(matrix(rnorm(10000 * 2), ncol = 2), local({
  r = runif(10000, 0, 2 * pi)
  0.5 * cbind(sin(r), cos(r))
}))
x = as.data.frame(x[sample(nrow(x)), ])
plot(x,pch=".")

> polyroot(c(40,0,0,5,20,10))
[1]  0.7747767+0.7263645i -0.7747767+1.0830293i -0.7747767-1.0830293i
[4]  0.7747767-0.7263645i -2.0000000+0.0000000i
>