R help - Jan 2012 - What is wrong with this plotting?

Hello

I have a data frame, called input, like this:

           DateTime CO2_A1cont
1 2011-04-08 11:47:01         NA
2 2011-04-08 12:42:01    8.90000
3 2011-04-08 13:07:01         NA
4 2011-04-08 13:32:01         NA
5 2011-04-08 13:57:01   7.556482
6 2011-04-08 14:22:01         NA
....
57 2011-04-09 16:52:01   4.961558

And like to plot this series with plot() and connected lines, no interruption by
the NAs.
I found that this code works:

y<-input[,2]
times <- DateTime

plot(y~as.POSIXct(times, format="%d.%m. %H:%M"), type="l",
data=na.omit(data.frame(y,times)))

whereas this plot command...

 plot(input[,2]~as.POSIXct(DateTime, format="%d.%m. %H:%M"),
type="l", data=na.omit(data.frame(input[,2],DateTime)))

... produces the error:

Error in model.frame.default(formula = input[, 2] ~ as.POSIXct(DateTime,  :
  variable lengths differ (found for 'as.POSIXct(DateTime, format =
"%d.%m. %H:%M")')

I already checked the length of y, times, input[,2], DateTime,
as.POSIXct(DateTime, format="%d.%m. %H:%M") which give all 57!
nrow(data.frame(input[,2],DateTime)) and nrow(data.frame(y,times)) give both 
57! Too.

Thanks for any help.

Best regards

Raphael


	[[alternative HTML version deleted]]

On Fri, Jan 6, 2012 at 5:49 AM,  <raphael.felber at art.admin.ch>
wrote:
> Hello
>
> I have a data frame, called input, like this:
>
> ? ? ? ? ? DateTime CO2_A1cont
> 1 2011-04-08 11:47:01 ? ? ? ? NA
> 2 2011-04-08 12:42:01 ? ?8.90000
> 3 2011-04-08 13:07:01 ? ? ? ? NA
> 4 2011-04-08 13:32:01 ? ? ? ? NA
> 5 2011-04-08 13:57:01 ? 7.556482
> 6 2011-04-08 14:22:01 ? ? ? ? NA
> ....
> 57 2011-04-09 16:52:01 ? 4.961558
>
> And like to plot this series with plot() and connected lines, no
interruption by the NAs.
> I found that this code works:
>
> y<-input[,2]
> times <- DateTime
>
> plot(y~as.POSIXct(times, format="%d.%m. %H:%M"),
type="l", data=na.omit(data.frame(y,times)))
>
> whereas this plot command...
>
> ?plot(input[,2]~as.POSIXct(DateTime, format="%d.%m. %H:%M"),
type="l", data=na.omit(data.frame(input[,2],DateTime)))
>
> ... produces the error:
>
> Error in model.frame.default(formula = input[, 2] ~ as.POSIXct(DateTime, ?:
> ?variable lengths differ (found for 'as.POSIXct(DateTime, format =
"%d.%m. %H:%M")')
>
> I already checked the length of y, times, input[,2], DateTime,
as.POSIXct(DateTime, format="%d.%m. %H:%M") which give all 57!
nrow(data.frame(input[,2],DateTime)) and nrow(data.frame(y,times)) give both
?57! Too.
Try this reading DF into a zoo object.  (tz="" has the effect of
setting its index to POSIXct using the current time zone -- you might
need tz = "GMT" depending on what you want):

library(zoo)
z <- read.zoo(DF, tz = "")
plot(na.approx(z))


Assuming DF is:

DF <- structure(list(DateTime = structure(1:6, .Label = c("2011-04-08
11:47:01",
"2011-04-08 12:42:01", "2011-04-08 13:07:01",
"2011-04-08 13:32:01",
"2011-04-08 13:57:01", "2011-04-08 14:22:01"), class =
"factor"),
    CO2_A1cont = c(NA, 8.9, NA, NA, 7.556482, NA)), .Names =
c("DateTime",
"CO2_A1cont"), class = "data.frame", row.names = c(NA, -6L))


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