Subset()

Hi Jim,

I'm really sorry to bother you, but finally I have another problem, then
when I try to make a plot

plot(Soil_Temp_Avg~DateTime,eldf2)

I have an error message saying :
Error in (function (formula, data = NULL, subset = NULL, na.action =
na.fail, : invalid type (list) for variable 'DateTime'


2017-01-22 3:42 GMT+01:00 Elise LIKILIKI <elise.likiliki at gmail.com>:

Hi Jim,

Thank you so much, it works with your method !! I'm going to be able to
process my data, thanks again !

Regards,

Elise

2017-01-21 23:32 GMT+01:00 Jim Lemon <drjimlemon at gmail.com>:

Hi Elise,
If I create a CSV file like your example and read it into a data frame:

eldf<-read.csv("el.csv")

Then convert the first field to POSIXt dates:

eldf$DateTime<-strptime(eldf$DateTime,"%Y-%m-%d %H:%M:%S")
class(eldf$DateTime)
[1] "POSIXlt" "POSIXt"

I can subset the file like this:

time_after<-strptime("2017-01-09 18:00:00","%Y-%m-%d %H:%M:%S")

time_after

[1] "2017-01-09 18:00:00 AEDT"

eldf[eldf$DateTime >= time_after,]

            DateTime RECORD PTemp PPFD_Avg Air_Temp_Avg RH_avg Soil_Temp
7  2017-01-09 18:00:00      6 21.26   -48.83       -38.49 -0.415
79
8  2017-01-09 18:15:00      7 21.21   -52.23       -39.00 -0.642
79
9  2017-01-09 18:30:00      8 21.12   -54.68       -39.41 -0.805
79
10 2017-01-09 18:45:00      9 21.04   -56.44       .39.74 -0.939
79
11 2017-01-09 19:00:00     10 20.99   -57.71       -40.01 -1.046
79
12 2017-01-09 19:15:00     11 20.91   -58.66       -40.25 -1.137
79
13 2017-01-09 19:30:00     12 21.83   -59.39       -40.46 -1.208
79

Perhaps this will do what you want.

No need to apologize for your English, I could not make myself
understood in French.

Jim

On Sun, Jan 22, 2017 at 4:15 AM, Elise LIKILIKI
<elise.likiliki at gmail.com> wrote:

Hi Jim,

Yes exactly it returns "POSIXct" "POSIXt"
Find attached a screenshot showing my data in "data" object.
I don't need the data before 2017-01-10 11:00:00 nor columns : Records
and
Ptemp.
I've tried with subset() and with [ ] but I still have some rows
containing
data before 2017-01-10 11:00:00.

I'm french so I am really sorry about my english

2017-01-21 11:41 GMT+01:00 Jim Lemon <drjimlemon at gmail.com>:

Hi Elise,.
I would ask:

class(data$DateTime)

and see if it returns:

"POSIXct" "POSIXt"

Jim


On Sat, Jan 21, 2017 at 3:02 AM, Elise LIKILIKI
<elise.likiliki at gmail.com> wrote:

Hello,

I have a dataset containing Date Time, Air Temperature, PPFD, Sol
Temperature...
The first data are false so I would like to extract the other ones.
I've tried :

data1<-subset(data,DateTime>=as.POSIXct("2017-01-10

11:00:00",format="%Y-%m-%d


%H:%M:%S"),select=c(DateTime,PPFD_Avg,Air_Temp_Avg,RH_Avg,Soil_Temp_Avg))
But I still have 4 rows with data from 2017-01-10 10:00:00 to
2017-01-10
10:45:00 and I don't understand why.

Does anyone could help me please.

Thanks,

Elise LIKILIKI

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