[R] Problem in conversion of regulate time series and forecasting using Date Time [Timestamp values]:R

[Jeff Newmiller]

gg$timestamps <- as.POSIXct(as.character( gg$timestamps ) )

Factors are integers with the appearance of character data, so you are converting the integers to POSIXct. I usually try to avoid letting R automatically convert character data to factors, e.g. using stringsAsFactors=FALSE in read.csv so I don't have to convert them back from factors to manipulate them. 
-- 
Sent from my phone. Please excuse my brevity.

On April 27, 2017 9:32:44 PM PDT, Dhivya Narayanasamy <dhiv.shreya at gmail.com> wrote:
>Hi Jim,
>
>Thank you for the reply. 'gg.ts' is actually the object name of the
>time
>series I am using here.  Also I have changed my timestamp class from
>factor
>to POSIXct  (gg$timestamps <- as.POSIXct(gg$timestamps, format =
>"%Y-%m-%d
>%H-%M-%S") . When i plot this time series on graph, the x axis scales
>shows
>random value rather than showing timestamp value. Is there any way to
>correct the graph to make it show the timestamp value on x axis?  I use
>plotly function for plotting.
>
>Regards| Mit freundlichen Grüßen,
>
>Dhivya Narayanasamy
>
>Contact No: +91-8438505020
>
>On Fri, Apr 28, 2017 at 3:19 AM, Jim Lemon <drjimlemon at gmail.com>
>wrote:
>
>> Hi Dhivya,
>> I'm not that familiar with the "gg.ts" function, but you are passing
>> character values to the "frequency" and "start" arguments. If there
>is
>> no automatic conversion to numeric values, that would cause the
>error.
>> Similarly, your "timestamps" variable may have been read in as a
>> factor, which often causes trouble with date conversions. Try
>> as.character(gg$timestamps) instead of just gg$timestamps.
>>
>> Jim
>>
>>
>> On Thu, Apr 27, 2017 at 4:51 PM, Dhivya Narayanasamy
>> <dhiv.shreya at gmail.com> wrote:
>> > Hi,
>> > I am new to R. Kindly help me with the plot that gives wrong x-axis
>> > values.  I have a data frame "gg", that looks like this:
>> >
>> >> head(gg)
>> >
>> >            timestamps      value
>> > 1 2017-04-25 16:52:00 -0.4120000
>> > 2 2017-04-25 16:53:00 -0.4526667
>> > 3 2017-04-25 16:54:00 -0.4586667
>> > 4 2017-04-25 16:55:00 -0.4606667
>> > 5 2017-04-25 16:56:00 -0.5053333
>> > 6 2017-04-25 16:57:00 -0.5066667
>> >
>> > I need to plot this as a Time series data to do forecasting. The
>steps
>> are
>> > as follows:
>> >
>> > 1) gg$timestamps <- as.POSIXct(gg$timestamps, format = "%Y-%m-%d
>> %H-%M-%S")
>> >  #changing "Timestamps" column 'factor' to 'as.POSIXct'.
>> >
>> > 2) gg.ts <- xts(x=gg$value, order.by = gg$timestamps) #converting
>the
>> > dataframe to time series (Non Regular Time series)
>> >
>> > 3) fitting <- auto.arima(gg.ts) #fitting the time series model
>using
>> > auto.arima
>> >
>> > 4) fore <- forecast(fitting, h=30, level = c(80,95))  #Forecasting
>> >
>> > 5) I am using plotly to this forecast model (Inspired from here :
>> > https://plot.ly/r/graphing-multiple-chart-types/#
>> plotting-forecast-objects)
>> >
>> > plot_ly() %>%
>> >   add_lines(x = time(gg.ts), y = gg.ts,
>> >             color = I("black"), name = "observed") %>%
>> >   add_ribbons(x = time(fore$mean), ymin = fore$lower[, 2], ymax =
>> > fore$upper[, 2],
>> >               color = I("gray95"), name = "95% confidence") %>%
>> >   add_ribbons(x = time(fore$mean), ymin = fore$lower[, 1], ymax =
>> > fore$upper[, 1],
>> >               color = I("gray80"), name = "80% confidence") %>%
>> >   add_lines(x = time(fore$mean), y = fore$mean, color = I("blue"),
>name =
>> > "prediction")
>> >
>> >
>> > The plot comes out wrong: 1) x axis labels are wrong. It shows some
>> > irrelevant values on axis. 2) the plot is not coming out.
>> > Also I tried to convert "gg.ts" to a regulate time series which
>throws
>> > error :
>> >
>> >> gg.xts <- ts(gg.ts, frequency = '1', start = ('2017-04-25
>16:52:00'))
>> > Error in 1/frequency : non-numeric argument to binary operator
>> >
>> > Please help me how to use Date Time values in converting to
>regulate time
>> > series for forecasting.
>> >
>> >
>> > Regards
>> >> Dhivya
>> >
>> >         [[alternative HTML version deleted]]
>> >
>> > ______________________________________________
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>> posting-guide.html
>> > and provide commented, minimal, self-contained, reproducible code.
>>
>
>	[[alternative HTML version deleted]]
>
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