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
> 

integrate( )

> f<-function(x){1/log(x)}

> integrate(f,lower=0,upper=1)

Error in integrate(f, lower = 0, upper = 1) : non-finite function value

> 

> f<-function(x){1/log(x)}

> integrate(f,lower=0,upper=1)

Error in integrate(f, lower = 0, upper = 2) : non-finite function value

> 

> 

> p<-function(x){log(x)}

> integrate(p,lower=0,upper=1)

-1 with absolute error < 1.1e-15

> integrate(dnorm,-Inf,Inf)
1 with absolute error < 9.4e-05
>