T-T - 10 months ago 33

R 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`

`zoo`

`df2 <- as.yearmon(df1$Date, "%b-%y")`

`NA`

Answer

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 A B C 1 Jan 2000 2 1 3 2 Feb 2000 1 2 1 3 Mar 2000 2 1 3`

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))`

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`

Source (Stackoverflow)