Subsetting a dataframe based on the values of two or more columns

Question

I would like to subset a timeseries dataframe based on my requirement. I have a dataframe something similar to the one mentioned below.

> df
Date         Year     Month    Day   Time      Parameter
2012-04-19   2012     04       19    7:00:00   26
2012-04-19   2012     04       19    7:00:00   20
.................................................
2012-05-01   2012     05       01    00:00:00  23
2012-05-01   2012     05       01    00:30:00  22
.................................................
2015-04-30   2015     04       30    23:30:00  20
.................................................
2015-05-01   2015     05       01    00:00:00  26

From the dataframe similar to this I will like to select all the data from the first of May 2012 2012-05-01 to the end of April 2015-04-30 , regardless of the starting and end date of the dataframe .

However, I am familiar with the grep function to select the data from one particular column. I have been using the following code with grep and with .

# To select one particular year
> df.2012 <- df[grep("2012", df$Year),]
# To select two or more years at the same time
> df.sel.yr <- df[grep("201[2-5]", df$Year),]
# To select one particular month of a particular year. 
> df.Dec.2012 <- df[with(df, Year=="2012" & Month=="12"), ] 

With several Lines of commands i will be able to do it. But it would save a lot of time if I can do it with only few or one line of command.

Any help will be appreciated. Thank you in advance.

Answer 1

If your date column is not of class date first convert it to one by,

df$Date <- as.Date(df$Date)

and then you can subset the date by,

df[df$Date >= as.Date("2012-05-01") & df$Date <= as.Date("2015-04-30"), ]

#  Date       Year Month Day     Time     Parameter
#3 2012-05-01 2012     5   1   00:00:00        23
#4 2012-05-01 2012     5   1   00:30:00        22
#5 2015-04-30 2015     4  30   23:30:00        20