Plot a histogram of yearly counts Strptime()

General
1

Hello, I have a csv file that consists of one column. The column presents the date of posting on a website. I want to plot a histogram to see how the number of posts varies over the years. The file contains the years (2012 to 2016) and consists of 11,000 rows.

sample of the file:

2 30/1/12 21:07
3 2/2/12 15:53
4 3/4/12 0:49
5 14/11/12 3:49
6 11/8/13 16:00
7 31/7/14 8:08
8 31/7/14 10:48
9 6/8/14 9:24
10 16/12/14 3:34

The data types is dataframe
class(postsData) [1] "data.frame"

I tried converting the data to text using strptime function as below:

formatDate <- strptime(as.character(postsData$Date),format="“%d/%m/%y")

then plot the histogram

hist(formatDate,breaks=10,xlab="year")

image

Since this is a university assignment question I have to use strptime() to do the conversion and not any other function. The specification says:

you’ll need to convert from text values using the strptime() function. Instructions on how to use the function is available here:

R: Date-time Conversion Functions to and from Character

You will need to write a format string, starting with “%a %b” to tell the function how to parse the particular date/time format in your file. What format string do you need to use?

Thank you,

2

It seems like you have already managed to plot the requested histogram, could you explain what your specific problem is? Also please take a look to our homework policy, you are not supposed to include verbatim instructions.

3

Thanks for letting us know this is a homework question.

Firstly, your challenge with formatDate <- strptime(as.character(postsData$Date),format="“%d/%m/%y")
is

  • note the typo of the extra “ in the format argument
  • In format you need to get the right conversion specifications. Note the example, "16/12/14 3:34", that appears to be day/month/year hour:minute. Have a look at your link for all the conversation specifications.

Once you get the date-time extracted from the string, you want to extract just the year. Here's a good discussion of that: https://stackoverflow.com/questions/31973673/how-can-i-extract-year-from-strptime

4

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