How do I combine dates, regardless of a third variable in R? - r

Question

The following is a data example,
Month Year Tornado Location
January 1998 3 Illinois
February 1998 2 Illinois
March 1998 5 Illinois
January 1998 1 Florida
January 2010 3 Illinois
Here is what I want it to look like essentially,
Date Tornado
1998-01 4
1998-02 2
1998-03 5
2010-01 3
So, I want to combine the Year and Month into one, new column. The locations do not matter, I want to know the total number of tornadoes for January, 1998, and etc.
I have the following code, but do not know how to change it to incorporate both the variables I want, or if this is even the correct code for what I am attempting to do.
mydata$Date <- format(as.Date(mydata$month), "%m-%Y")
The real dataset is far too large to fix manually. I am basically attempting to make this data into time series data.

Answer 1

You need to apply some data transformation before applying How to sum a variable by group
aggregate(Tornado~Date, transform(df, Date = format(as.Date(paste(Month,Year,"01"),
"%B %Y %d"), "%Y-%m")), sum)
# Date Tornado
#1 1998-01 4
#2 1998-02 2
#3 1998-03 5
#4 2010-01 3
data
df <- structure(list(Month = structure(c(2L, 1L, 3L, 2L, 2L),
.Label = c("February", "January", "March"), class = "factor"),
Year = c(1998L, 1998L,1998L, 1998L, 2010L),
Tornado = c(3L, 2L, 5L, 1L, 3L), Location = structure(c(2L,
2L, 2L, 1L, 2L), .Label = c("Florida", "Illinois"), class = "factor")),
class = "data.frame", row.names = c(NA, -5L))

Answer 2

In the first place, I combined Month and Year into a single variable called Date, applied the appropriate format with zoo package, and grouped the results by Date.
library(tidyverse)
library(zoo)
df %>%
unite(Date, Month, Year) %>%
mutate(Date = as.yearmon(Date, format = '%B_%Y')) %>%
group_by(Date) %>%
summarise(Tornado = sum(Tornado))
# A tibble: 4 x 2
Date Tornado
<yearmon> <int>
1 Jan 1998 4
2 Feb 1998 2
3 Mar 1998 5
4 Jan 2010 3

Answer 3

if the day doesn't matter you can do:
#library (tidyverse)
library(lubridate)
x$Date<-as_date(paste0(x$Year,x$Month,"-01"))
# A tibble: 5 x 4
Month Year Tornados Date
<chr> <dbl> <dbl> <date>
1 January 1998 3 1998-01-01
2 February 1998 2 1998-02-01
3 March 1998 5 1998-03-01
4 January 1998 1 1998-01-01
5 January 2010 3 2010-01-01