# Learn R – How to Define Function in R

This article represents code examples in relation with how to write function in R. Please feel free to comment/suggest if I missed to mention one or more important points. Also, sorry for the typos.

• Function Definition
• Code Examples for Functions

###### How to Define Function

Function in R looks like following:

```# Function definition
funcName <- function( a, b, c ) {
return(v) # or simply v
}
# This is how a function is invoked
var1 <- funcName(x,y,x)
```

In above code, funcName is the name of the function. a, b, c are parameters. v is return variable

###### Code Examples for Functions

In the examples below, following four functions are demonstrated:

• Create an empty Data Frame
• Add/Append a vector to the data frame
• Search for a vector in the data frame
• Print first n rows in the data frame
```# Creates an empty Data Frame with two columns namely, Name and Age
# Return the newly created empty data frame with 0 row
createDF <- function() {
df <- data.frame(name=character(), age=numeric(), stringsAsFactors=F)
return(df)
}

# Add the vector, c, to the passed data frame, df
# Return the updated data frame
addToDF <- function( df, c) {
df[nrow(df) + 1,] <- c
return(df)
}

# Search the data frame for existence of values in vector cv
# Return true if found, else false
searchFromDF <- function( df, cv ) {
found <- F
for( i in 1:nrow(df) ) {
if( df\$name[i] == cv && df\$age[i] == cv ) {
found <- T
break
}
}
found
}

# Print first n rows of the dataframe
for( i in 1:nrow(df)) {
if( i < n+1) {
cat(df[i,]\$name,"\t",df[i,]\$age,"\n")
}
}
}
```

Following is how the above functions would be invoked:

```# Creates an empty data frame
df1 <- createDF()

# Add the vector to the the data frame

# Prints True
searchFromDF(df1, c("Aiyana", 9))
# Prints False
searchFromDF(df1, c("Anisha", 41))

# Prints first 2 rows of the dataframe df1 