Hello,
That's not the error I've had. You must be aware that read.table creates
a data.frame and therefore the object 'timestamps' is NOT holding time
stamps, it's holding a vector, 'V1', of time stamps.
timestamps <- read.table(text="
12:19:00
09:30:00
16:56:00
01:56:00
10:44:00
10:31:00
02:14:00
05:05:00
12:52:00
21:50:00
", stringsAsFactors=FALSE)
str(timestamps)
timestamps <- as.POSIXct(timestamps$V1, format="%H:%M:%S") # here
h1 <- cut(timestamps, breaks="hour")
h2 <- cut(timestamps, breaks="15 mins")
op <- par(mfrow=c(1, 2))
hist(as.integer(h1))
hist(as.integer(h2))
par(op)
And the rest works.
Rui Barradas
Em 17-07-2012 07:11, e-letter escreveu:
On 16/07/2012, Rui Barradas <ruipbarra...@sapo.pt> wrote:
Hello,
Em 16-07-2012 22:45, e-letter escreveu:
On 16/07/2012, r-help-requ...@r-project.org
<r-help-requ...@r-project.org> wrote:
> ------------------------------
>
> Message: 77
> Date: Mon, 16 Jul 2012 10:48:39 +0100
> From: Rui Barradas <ruipbarra...@sapo.pt>
> To: e-letter <inp...@gmail.com>
> Cc: r-help@r-project.org
> Subject: Re: [R] histogram of time-stamp data
> Message-ID: <5003e377.3000...@sapo.pt>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>
> timestamps <- as.POSIXct(Sys.Date()) + sample(24*60*60, 1e3, TRUE)
>
Why is it necessary to apply the sample to the current date? Looking
at the dataframe, I noticed that values have been changed:
No! That instruction is just to create a data example with more
date/time values, in this case with a total of 1e3 different values.
What's important is the way to plot the histogram, namely, the cut()
with two example time periods, and that hist() needs numbers, not cut's
levels.
With the original data provided, R reports an error, that "'x' must be numeric'.
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