Solving for loop in a data frome

I am working on a data frame and have extracted on the of the columns with hour data from 0 t0 23. I am adding one more column as type of the day based on hour. I had executed below for loop but getting error. Can somebody help me what is wrong with below syntax and how to correct the same.

for(i in data$Requesthours) {
   if(data$Requesthours>=0 & data$Requesthours<3) {
     data$Partoftheday <- "Midnight"
   } else if(data$Requesthours>=3 & data$Requesthours<6) {
     data$Partoftheday <- "Early Morning"
   } else if(data$Requesthours>=6 & data$Requesthours<12) {
     data$Partoftheday <- "Morning"
   } else if(data$Requesthours>=12 & data$Requesthours<16) {
     data$Partoftheday <- "Afternoon"
   } else if(data$Requesthours>=16 & data$Requesthours<20) {
     data$Partoftheday <- "Evening"
   } else if(data$Requesthours>=20 & data$Requesthours<=23) {
     data$Partoftheday <- "Night"
   }
}