R Programming Syntax Quickstart

If you have ANY programming experience in other languages, this guide will get you started in R very quickly.

Logic Operators

a == b	a equals b
a != b	a is not equal to b
a > b	a is greater than b
a < b	a is less than b
a >= b	a is greater than OR equal to b
a <= b	a is less than OR equal to b
(condition 1) & (condition 2)	(condition 1) AND (condition 2)
(condition 1) | (condition 2)	(condition 1) OR (condition 2)

Also, try the following to understand "&&" and "||":

> a<-c(1:10) > b<-a > c<-b > c[1:4]<-.5 > (a == b) && (a > c)
[1] TRUE
> (a == b) & (a > c)
[1] TRUE TRUE TRUE TRUE FALSE FALSE FALSE FALSE FALSE FALSE
> (a == b) | (a > c)
[1] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
> (a == b) || (a > c)
[1] TRUE


IF statements

The general example:

if( condition ) {

} else if( other condition ){

} else {

}


The specific example:

a<-55
if( a <= 54.9 ) {
   print("a is less than or equal to 54.9")
} else if( a == 55 ){
   print("a equals 55")
} else {
   print("a is greater than 54.9 and not 55")
}

For Loops

The general example:

for(variable in vector) {

}



Specific examples:

#example 1
for(i in 1:10) {
   print(i)
}

#example 2
index.vector<-c(4,3,7,5)
numberz<-runif(10)
print(numberz)

for(i in index.vector) {
   print(numberz[i])
}

#example 3
for(i in 1:10) {
   if(i == 3) {
      next
   } else if(i == 7) {
      break
   }
   print(i)
}

#example 4
mat<-matrix(0,3,4)
print(mat)

for(i in 1:3) {
   for(j in 1:4) {
      mat[i,j]<-rnorm(1)
   }
}



While Loops

General Example:

while(condition) {

}

Note that you must something write something within the while that will update at least one of the variables in the condition. Otherwise, you could have a perpetual loop.

Specific Example:

i<- -1
while( i < 10) {
    print(i)
    i<-i+1 
}

Repeat Loop

In a repeat loop, you not only explicitly update variables, you must also explicitly test the condition.
Specific Example:

i<- -1
repeat{
   print(i)
   i<-i+1
   if( i == 10) {
      break
   }
}


Functions

For example, you could have a function that evaluates a formula. A function can call other functions.

General Example:

function_name<-function(parameters) {


   return(return_variable)
}


Specific Example:

calcQuadratic<-function(a, b, c, x) {
   y<-a*x*x+b*x+c
   return(y)
}

calcQuadratic(2,3,5,.07)

my.var<-calcQuadratic(3.32,7.6,5.999,3.2)
print(my.var)



BANG!!