You could make a little filter for each one, and omit NAs values.
na.omit(FDataZ) # omit NAs values of all data frame. You can select expecific variables whit $. e.g . na.omit(FDataZ$Length_z)
library(dplyr)
filter(FDataZ, AgeLet <= 64) #You can select the number of filter.
filter(FDataZ, AgeLet >= 60)
Would I be able to filter NAs in multiple categories with this? If so, how would I format it?
filtered_data <- FDataZ %>% dplyr::filter(!AgeLet %in% '')
Use na.omit(FDataZ) and it will drop all rows containing an NA. Use with caution though - if you have lots of NAs in your data, you may end up throwing away more data you would wish to!