Dear help list - I have light data with 5-min time-stamps. I would like to
insert four 1-min time-stamps between each row and interpolate the light data
on each new row. To do this I have come up with the following code:
lightdata <- read.table("Test_light_data.csv", header = TRUE, sep = ",") #
read data file into object "lightdata"
library(chron)
mins <- data.frame(times(1:1439/1440)) # generate a dataframe of 24 hours of
1-min timestamps
Nth.delete <- function(dataframe, n)dataframe[-(seq(n, to=nrow(dataframe),
by=n)),] # function for deleting nth row
empty <- data.frame("1/9/13", Nth.delete(mins, 5), "NA") # delete all 5-min
timestamps in a new dataframe
colnames(empty) <- c("date", "time", "light") # add correct column name to
empty timestamp dataframe
newdata <- rbind(lightdata, empty)
I get the following error message:
Warning message:
In `[<-.factor`(`*tmp*`, ri, value = c(0.000694444444444444,
0.00138888888888889, :
invalid factor level, NAs generated
Digging into this a little, I can see that the two time columns are doing what
I need and APPEAR to be similar in format:
> head(lightdata)
date time light
1 1/9/13 0:00:00 -0.00040925
2 1/9/13 0:05:00 -0.00023386
3 1/9/13 0:10:00 -0.00032155
4 1/9/13 0:15:00 -0.00017539
5 1/9/13 0:20:00 -0.00029232
6 1/9/13 0:25:00 -0.00038002
> head(empty)
date time light
1 1/9/13 00:01:00 NA
2 1/9/13 00:02:00 NA
3 1/9/13 00:03:00 NA
4 1/9/13 00:04:00 NA
5 1/9/13 00:06:00 NA
6 1/9/13 00:07:00 NA
but they clearly are not as far as R is concerned, as shown by str:
> str(lightdata)
'data.frame': 288 obs. of 3 variables:
$ date : Factor w/ 1 level "1/9/13": 1 1 1 1 1 1 1 1 1 1 ...
$ time : Factor w/ 288 levels "0:00:00","0:05:00",..: 1 2 3 4 5 6 7 8 9 10 ...
$ light: num -0.000409 -0.000234 -0.000322 -0.000175 -0.000292 ...
> str(empty)
'data.frame': 1152 obs. of 3 variables:
$ date : Factor w/ 1 level "1/9/13": 1 1 1 1 1 1 1 1 1 1 ...
$ time :Class 'times' atomic [1:1152] 0.000694 0.001389 0.002083 0.002778
0.004167 ...
.. ..- attr(*, "format")= chr "h:m:s"
$ light: Factor w/ 1 level "NA": 1 1 1 1 1 1 1 1 1 1 ...
In the first (original) dataframe, light is a factor, while in the dataframe of
generated timestamps, the timestamps are actually still in fractions of a day.
Presumably this is why rbind is not working? Can anyone help? By the way, I
know I can use na.approx in zoo to do the eventual interpolation of the light
data. It's getting there that has me stumped for now.
Many thanks, Jon (new R user).
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