在R数据框中按月和年排序

Question

I have cleaned and ordered my data by date, which looks like below:

df1 <- data.frame(matrix(vector(),ncol=4, nrow = 3))
colnames(df1) <- c("Date","A","B","C")
df1[1,] <- c("2000-01-30","0","1","0")
df1[2,] <- c("2000-01-31","2","0","3")
df1[3,] <- c("2000-02-29","1","2","1")
df1[4,] <- c("2000-03-31","2","1","3")
df1
        Date  A  B  C
1 2000-01-30  0  1  0
2 2000-01-31  2  0  3
3 2000-02-29  1  2  1
4 2000-03-31  2  1  3

However, I want to drop the day and order the data by month and year so the data will look like:

        Date  A  B  C
1    2000-01  2  1  3
3    2000-02  1  2  1
4    2000-03  2  1  3

I tried to use as.yearmon from zoo df2 <- as.yearmon(df1$Date, "%b-%y") and it returns NA . Thank you in advance for your generous help!

Answer 1

Here's a way to get the sum of the values for each column within each combination of Year-Month:

library(zoo)
library(dplyr)

# Convert non-date columns to numeric
df1[,-1] = lapply(df1[,-1], as.numeric)

df1 %>% mutate(Date = as.yearmon(Date)) %>%
  group_by(Date) %>%
  summarise_each(funs(sum))

Or, even shorter:

df1 %>% 
  group_by(Date=as.yearmon(Date)) %>%
  summarise_each(funs(sum))

  Date ABC 1 Jan 2000 2 1 3 2 Feb 2000 1 2 1 3 Mar 2000 2 1 3 

A couple of additional enhancements:

1. Add the number of rows for each group:

    df1 %>% group_by(Date=as.yearmon(Date)) %>% summarise_each(funs(sum)) %>% bind_cols(df1 %>% count(d=as.yearmon(Date)) %>% select(-d)) 

2. Multiple summary functions:

    df1 %>% group_by(Date=as.yearmon(Date)) %>% summarise_each(funs(sum(.), mean(.))) %>% bind_cols(df1 %>% count(d=as.yearmon(Date)) %>% select(-d)) 

  Date A_sum B_sum C_sum A_mean B_mean C_mean n 1 Jan 2000 2 1 3 1 0.5 1.5 2 2 Feb 2000 1 2 1 1 2.0 1.0 1 3 Mar 2000 2 1 3 2 1.0 3.0 1 

Answer 2

Your Date column is a character vector, when it needs to be a Date type vector. So:

df1$Date <- as.Date(df1$Date)
df1$Date <- as.yearmon(df1$Date)

      Date A B C
1 Jan 2000 0 1 0
2 Jan 2000 2 0 3
3 Feb 2000 1 2 1
4 Mar 2000 2 1 3