Filling data down to subsequent row - r

Question

I have data that look similar to:
Alabama Age>50 Value1 Value2 Value3
Age<50 Value1 Value2 Value3
Alaska Age>50 Value1 Value2 Value3
Age<50 Value1 Value2 Value3
I only need to keep the data for Age<50. How can I repeat the state name to the row below it? I have created a string of the state names, but am unsure how to insert it into every other row in the first column.
The head of my data.frame is:
d <- structure(c("ALABAMA", "", "ALASKA", "", "ARIZONA", "", "Under 18",
"Total all ages", "Under 18", "Total all ages", "Under 18", "Total all ages",
"0", "1", "10", "87", "46", "303", "0", "0", "0", "36", "6", "855", "84,843",
"", "469,145", "", "6,303,555", ""), .Dim = c(6L, 5L), .Dimnames = list(NULL,
c("State", "", "Rape3", "Prostitution and\ncommercialized\nvice",
"2014\nestimated \npopulation")))

Answer 1

How's this:
df <- as.data.frame(structure(c("ALABAMA", "", "ALASKA", "", "ARIZONA", "", "Under 18", "Total all ages", "Under 18", "Total all ages", "Under 18", "Total all ages", "0", "1", "10", "87", "46", "303", "0", "0", "0", "36", "6", "855", "84,843", "", "469,145", "", "6,303,555", ""), .Dim = c(6L, 5L), .Dimnames = list(NULL, c("State", "", "Rape3", "Prostitution and\ncommercialized\nvice", "2014\nestimated \npopulation"))), stringsAsFactors = FALSE)
names(df)[5] <- "est_pop"
df$est_pop[df$est_pop == ""] <- NA
df$State[df$State == ""] <- NA
library(zoo)
df$State <- na.locf(df$State,na.rm = TRUE)
df$est_pop <- na.locf(df$est_pop,na.rm = TRUE)
df <- df[df$V2 == "Total all ages" , ]

Answer 2

Supposing you have a column header Age
Supposing your data is called MyDataFrame
You could use for example:
# Load required package zoo
if(library("zoo", logical.return=TRUE, quietly=TRUE, warn.conflicts = FALSE)==FALSE){
install.packages("zoo")
} else{require("zoo") }
MyDataFrame$Age<-na.locf(MyDataFrame$Age, na.rm=FALSE)
Hope it helps.