######
## Abbrivations

len <- length
f <- `function` #### DOESN'T WORK


######
## BASIC

## If
a <- 3
if(a==3) print("is 3") else print("not 3")

## For
for(i in 1:10) print(i)


#####
## Errors

## Stop on error
stop ("error happend")

## null?
is.null(NULL)



#####
## Data Structures

## Vector
num3to5 <- c(3,4,5)
numTo10 <- 1:10

## Matrix
ones <- rep(1,times=9)
m1 <- matrix(ones, nrow=3, ncol=3, byrow = FALSE)

## number of rows
nrow(m1) 


## List of matrices
matrices <- list(m1, m1, m1)
firstm <- matrices[[1]]



#####
## MISC

## sum, max, 
sum(1:10)
max(1:10)

## String
paste("a", "b")
cat(c(1,2))


####
## MATH MISC

## transpose matrix
t(m1) 

## random sample
sample(1:10, 1)



## Apply

## List (of matrices)




######
## HIGH LEVEL FUNCTIONS


## apply
apply(statex77, 2, median) # 2:bycolumn 1:byrow

## apply2
m <- matrix(c(1:10, 11:20), nrow = 10, ncol = 2)
# divide all values by 2
apply(m, 1:2, function(x) x/2)

## which
which(1:10 == 3)

## Filter
gr3 <- function(x) if(x>3) return(TRUE) else return(FALSE)
num4to10 <- Filter(gr3, 1:10)

## Map
nums <- unlist( Map(sqrt, 1:10) )

## Map - Reduce
nums_string <- Reduce(paste, Map(sqrt, 1:10) )


## mapply


## sapply (simple)
sapply(3:5, function(i)i+1)


## lapply (list)

## reading numbers

## further apply stuff:
### http://nsaunders.wordpress.com/2010/08/20/a-brief-introduction-to-apply-in-r/