RinAction - R Data Manipulation - missing variables

gistfile1.r

#############################################################################
##    -------------------   Missing Values  ----------------------###########
## 1. missing values in R are represented as NA (not available)             #
## 2. Impossible values (devided by 0) are represented as NaN (not a number)#
#############################################################################

# Identify missing values using is.na() function
is.na(leadership[6:9])

y <- c(1,2,3,NA)
is.na(y)

# Calculate vector length with missing (NAs)
a <- c(1,2,3,NA,NA,2,NA)
length(a[!is.na(a)])
length(na.omit(a))   
sum(!is.na(a))

# Recode extreme/incorrect values to missing
leadership[leadership$age == 99, "age"] <- NA
leadership

# Math calculation without missing
x <- c(1,2,NA,3)
y <- x[1] + x[2] + x[3] + x[4]
z <- sum(x)
# both y and z should b NA

y <- sum(x,na.rm=TRUE)

# Delete missing observations/records using the na.omit() function
newdata <- na.omit(leadership)
newdata