R使用向量中的项循环过滤数据

Question

I am attempting to speed some process up, so that I do not have to edit the year manually each time. I am certainly no expert in R, not sure if this is too easy to ask. It seems like it works for the first item in the vector, since the result is right.

I would like to print the amount of rows in a filtered dataset, for each year. library(dplyr)

getData <- function(){
  data <- read.csv("data.csv", stringsAsFactors=FALSE)
}

data <- getData()
years <- c("2010", "2011", "2012", "2013", "2014", "2015", "2016")
nbh <- "SomeVar"

for(year in years){
  data <- filter(data, grepl(year, Created.Date) & grepl(nbh, SomeColumn))
  print(nrow(data))
}

However, it just outputs this, where the first one is correct:

[1] 2
[1] 0
[1] 0
[1] 0
[1] 0
[1] 0
[1] 0

Is this because it filters the data the first time, it then has only two records, which causes for the next ones to be 0?

Answer 1

You can probably modify this to fit your bill.

library(dplyr)

xy <- data.frame(letters = sample(letters, 100, replace = TRUE),
                 years = sample(seq(from = 2010, to = 2015, by = 1), size = 100, replace = TRUE),
                 values = rnorm(100))

xy %>%
  group_by(years) %>%
  filter(letters %in% c("a", "b", "c")) %>%
  count()

# A tibble: 6 × 2
  years     n
  <dbl> <int>
1  2010     5
2  2011     2
3  2012     3
4  2013     1
5  2014     1
6  2015     3

Answer 2

You're overwriting your dataset in your for loop. Try

for(year in years){
  data_temp <- filter(data, grepl(year, Created.Date) & grepl(nbh, SomeColumn))
  print(nrow(data_temp))
}