ggplot: plotting against time on multiple dates

Question

I want to plot a line graph, with x axis time (hh:mm)(this is a specific time interval), and y axis average price.

I want the graph to display multiple lines (one line for each day).

Currently my data frame is like this (I have some other variables as well but I am not using them in my graph. the relevant ones are below):

AV.PRICE DATE        TIME
180      2014-01-20  13H 0M 0S
179      2014-01-20  13H 1M 0S
175      2014-01-20  13H 2M 0S
179      2014-01-20  13H 3M 0S

...and so on, the dates continue but the times only take on values between 13:00 and 15:00 each day

The DATE class is date, AV.PRICE is num, TIME is period (used lubridate)

if my question isnt clear, this is what i'm looking for, plotting a date-agnostic graph on a time only axis, except i'm using ggplot2 in r: plotting data for different days on a single HH:MM:SS axis

EDITED:
when i try to plot the original df with ggplot, it does not recognize the time variable. ggplot(df, aes(x=TIME, y=AV.PRICE, group = DATE)) + geom_line() gives error: cannot compare Period to Duration

dput

structure(list(AV.PRICE = c(178.841368677043, 178.837478586724, 
178.811640304183, 178.8395125, 178.858236768802, 178.860812464589
), DATE = structure(c(16098, 16098, 16098, 16098, 16098, 16098
), class = "Date"), TIME = structure(c(0, 0, 0, 0, 0, 0), year = c(0, 
0, 0, 0, 0, 0), month = c(0, 0, 0, 0, 0, 0), day = c(0, 0, 0, 
0, 0, 0), hour = c(13, 13, 13, 13, 13, 13), minute = c(0, 1, 
2, 3, 4, 5), class = structure("Period", package = "lubridate"))), .Names = c("AV.PRICE", 
"DATE", "TIME"), row.names = c(NA, 6L), class = "data.frame")

it looks like your data already is in long format, what do you want to do with melt — Nate
when i try to plot the original df with ggplot, it does not recognize the time variable. ggplot(df, aes(x=TIME, y=AV.PRICE, group = DATE)) + geom_line() gives error: cannot compare Period to Duration: — shoestringfries
Maybe you can post the dput(df) in your question to see if there's somebody can help you with this. — Psidom
if i may ask, what is missing from my example? i have a sample of the data, i specified the classes of the variables, i provided the code i tried and the error message. do you need other information? — shoestringfries

Nate Nate · Accepted Answer · 2016-12-30T20:57:24

I think you problem is with having df$TIME class = "Period", instead of time. All you need to do it coerce it back to POSIXt.

df <- data.table::fread("AV.PRICE DATE        TIME
180      2014-01-20  13H0M0S
179      2014-01-20  13H1M0S
175      2014-01-20  13H2M0S
179      2014-01-20  13H3M0S
182      2014-01-21  13H0M0S
181      2014-01-21  13H1M0S
177      2014-01-21  13H2M0S
181      2014-01-21  13H3M0S")

I added an extra value for Date with shifted AV.PRICE for display purposes. Sorry I couldn't get your dput to load properly or I would have started from there. Also fread doesn't like spaces in the input, but you could use something like collapse and as.character on your actual df$TIME column.

df$TIME %<>% lubridate::parse_date_time("HMS") # make it class = "POSIXt

ggplot(data = df, aes(x = TIME, y = AV.PRICE, color = DATE)) +
    geom_line()

You could play around with + scale_x_time() if you want too, but the default looks like it is rendering your desired output.

ggplot: plotting against time on multiple dates

1 Answers