R : Copyright 2003, The R Development Core Team
Version 1.8.0  (2003-10-08)

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Type 'license()' or 'licence()' for distribution details.

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Type 'contributors()' for more information.

Type 'demo()' for some demos, 'help()' for on-line help, or
'help.start()' for a HTML browser interface to help.
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[Previously saved workspace restored]

> 7^2
[1] 49
> square <- function (x) x*x
> square
function (x) x*x
> square(7)
[1] 49
> 
> source("c:/quad.txt")
> quadratic
function (a,b,c)
{ d <- b^2 - 4*a*c
  c ((-b+sqrt(d))/(2*a), (-b-sqrt(d))/(2*a))
}
> quadratic(1,0,-2)
[1]  1.414214 -1.414214
> quadratic(5,3,-2)
[1]  0.4 -1.0
> quadratic(5,3,2)
[1] NaN NaN
Warning messages: 
1: NaNs produced in: sqrt(d) 
2: NaNs produced in: sqrt(d) 
>
> source("c:/quad.txt")
> quadratic
function (a,b,c)
{ d <- b^2 - 4*a*c
  if (d<0) stop("Discrimanent is negative")
  c ((-b+sqrt(d))/(2*a), (-b-sqrt(d))/(2*a))
}
> quadratic(5,3,2)
Error in quadratic(5, 3, 2) : Discrimanent is negative
>
> source("c:/quad.txt")
> quadratic
function (a,b,c)
{ d <- b^2 - 4*a*c
  c ((-b+sqrt(d+0i))/(2*a), (-b-sqrt(d+0i))/(2*a))
}
> quadratic(5,3,2)
[1] -0.3+0.5567764i -0.3-0.5567764i
> quadratic(1,0,-2)
[1]  1.414214+0i -1.414214+0i
>
> a<-9
>
> a<10
[1] TRUE
> a<=10
[1] TRUE
> a < 10 && a > 5
[1] TRUE
> a < 10 && a > 9
[1] FALSE
> a < 10 || a > 9
[1] TRUE
> 
> a <- c(4,7,8)
> 
> if (a<10) cat("fred\n")
fred
Warning message: 
the condition has length > 1 and only the first element will be used in: if (a < 10) cat("fred\n") 
> a < 10
[1] TRUE TRUE TRUE
> if (all(a<10)) cat("fred\n")
fred
> if (any(a<10)) cat("fred\n")
fred
> if (a>5) cat("fred\n")
Warning message: 
the condition has length > 1 and only the first element will be used in: if (a > 5) cat("fred\n") 
> 
> i <- 1
> while (i<=10) 
+ { print(i^2)
+   i <- i+1
+ }
[1] 1
[1] 4
[1] 9
[1] 16
[1] 25
[1] 36
[1] 49
[1] 64
[1] 81
[1] 100
>
> i <- 1
> while (i<=10) 
+ { cat(i^2,"\n")
+   i <- i+1
+ }
1 
4 
9 
16 
25 
36 
49 
64 
81 
100 
>
> for (i in 1:10) cat (i^2,"\n")
1 
4 
9 
16 
25 
36 
49 
64 
81 
100 
>
> i <- 1
> repeat
+ { cat(i,i^2,"\n")
+   if (i==10) break;
+   i <- i+1
+ }
1 1 
2 4 
3 9 
4 16 
5 25 
6 36 
7 49 
8 64 
9 81 
10 100 
>
> (1:10)^2
 [1]   1   4   9  16  25  36  49  64  81 100
> 
> n <- 10
> 
> for (i in 1:n) print(i^2)
[1] 1
[1] 4
[1] 9
[1] 16
[1] 25
[1] 36
[1] 49
[1] 64
[1] 81
[1] 100
> 
> n <- 1
> for (i in 1:n) print(i^2)
[1] 1
> 
> n <- 0
> 
> for (i in 1:n) print(i^2)
[1] 1
[1] 0
> 
> 1:10
 [1]  1  2  3  4  5  6  7  8  9 10
> 10:1
 [1] 10  9  8  7  6  5  4  3  2  1
> 1:0
[1] 1 0
> 
> m <- matrix(1:6, 3, 2)
> m
     [,1] [,2]
[1,]    1    4
[2,]    2    5
[3,]    3    6
> 
> apply(m,2,mean)
[1] 2 5
> apply(m,1,mean)
[1] 2.5 3.5 4.5