R Plot Histogram On Dataframe with dates-time object

Question

I have the following R dataframe with column Date and column Value, column Date is R chron objects (format <- "m/d/y h:m:s").

What I want to do is to visualize the time series data by ploting histogram or line chart, and I also want to specify the date-time range on x-axis (e.g. from 10/2/16 20:00:00 to 10/3/16 20:00:00). However after searching for the online guides I still do not have a clue.

Would anyone give me a sample code using ggplot or other package? I appreciate your help.

Date                 Value
(10/03/16 09:31:00)  180,912.00
(10/03/16 09:32:00)  112,359.00
(10/03/16 09:35:00)   93,539.00
(10/03/16 09:35:00)  156,283.00
(10/03/16 09:36:00)  226,704.00
(10/03/16 09:37:00)  780,094.00
(10/03/16 09:45:00)  184,632.00
(10/03/16 09:48:00)  144,984.00
(10/03/16 09:49:00)  311,035.00
(10/03/16 09:51:00)  210,653.00
(10/03/16 09:51:00)   72,626.00
(10/03/16 09:52:00)  241,173.00
(10/03/16 09:54:00)  233,416.00
(10/03/16 09:55:00)  146,550.00
(10/03/16 10:24:00)  331,191.00
(10/03/16 10:28:00)  107,015.00
(10/03/16 10:36:00)  196,162.00
(10/03/16 10:41:00)  466,879.00
(10/03/16 10:44:00)  294,589.00
(10/03/16 10:48:00)  164,339.00
(10/03/16 10:52:00)  137,082.00
(10/03/16 10:58:00)  180,667.00
(10/03/16 11:04:00)  259,475.00

Updated on 11/28/2016 6:35 pm With the help of yeedle's codes, I am able to plot the following:

ggplot(temp_merge_sub1, aes(x=Date, y=Value, group=1)) + geom_bar(stat = "identity")

GGPlot2

What I really want to improve from that is:

how to correctly set the breaks on y-axis?
how to set breaks on x-axis and display the histogram on the added up value in each of the 2-hour intervals?

Thank you for your help! I appreciate it!

You have multiple values for the same date-time. How do you want that to be displayed on the plot? — yeedle
– yeedle, Commented Nov 28, 2016 at 16:50
Thank you @yeedle for helping with my question. The data above is only a small portion of my data, and what I would like to show with histogram is kind of adding up the value within certain fixed time ranges (e.g. 2 hour breaks, 10/3/2016 6:00 - 8:00, 8:00-10:00, ... etc) and then how the histogram of added up value over each of the time intervals. I am not sure if ggplot2 could do that? — Huachen Qin
– Huachen Qin, Commented Nov 28, 2016 at 23:21
To do that you would can add a new column to your dataframe with the rounded time range (you can use the round_date function from lubridate), and then plot using the new column. Setting breaks and limits is done with scale_x_datetime. — yeedle
– yeedle, Commented Nov 29, 2016 at 0:02

yeedle · Accepted Answer · 2016-11-28 17:11:14Z

1

I converted Date to POSIXct objects, using lubridate's ymd_hms function.

library(ggplot2)
ggplot(df, aes(x=Date, y=Value)) + 
  geom_bar(stat="identity") + 
  scale_x_datetime(limits =c(mdy_hms("10/2/16 20:00:00"),mdy_hms("10/3/16 20:00:00")))

You get a clearer picture without the scale_x_datetime limits:

Simply replace geom_bar with geom_line for a line graph:

ggplot(df, aes(x=Date, y=Value)) + 
  geom_line()

edited Nov 28, 2016 at 17:11

answered Nov 28, 2016 at 16:56

yeedle

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3 Comments

Axeman Over a year ago

Or use geom_col instead.

Axeman Over a year ago

It's new yes. It's equivalent to geom_bar(stat = "identity").

yeedle Over a year ago

Thanks, I did not know that.

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