[R] Arrange data

[Jim Lemon]

Your problem is in the subset operation. You have asked for a value of
month greater or equal to 7 and less than or equal to 6. You probably
got an error message that told you that the data were of length zero
or something similar. If you check the result of that statement:

> mddat$month >= 7 & mddat$month <= 6
logical(0)

In other words, the two logical statements when ANDed cannot produce a
result. A number cannot be greater than or equal to 7 AND less than or
equal to 6. What you want is:

mddat2<-mddat[mddat$Year == 1975 & mddat$Month >= 7 |
 mddat$Year == 1976 & mddat$Month <= 6,]
mean(mddat2$Value)
[1] 88.91667

Apart from that, your email client is inserting EOL characters that
cause an error when pasted into R.

Error: unexpected input in "�"

Probably due to MS Outlook, this has been happening quite a bit lately.

Jim

On Mon, Aug 3, 2020 at 11:30 PM Md. Moyazzem Hossain
<hossainmm using juniv.edu> wrote:
>
> Dear Jim,
>
> Thank you very much. It is working now.
>
> However, I am also trying to find the average of the value from July 1975 to June 1976 and recorded as the value for the year 1975 but got an error message. I am attaching the data file here. Please check the attachment.
>
> mddat=read.csv("F:/mddat.csv", header=TRUE)
> mddat2<-mddat[mddat$Month >=7 & mddat$Month <= 6,]
> jan2jun<-by(mddat2$Value,mddat2$Year,mean)
> jan2jun
>
> Please help me again and many thanks in advance.
>
> Md
>
>
> On Mon, Aug 3, 2020 at 12:33 PM Rasmus Liland <jral using posteo.no> wrote:
>>
>> On 2020-08-03 21:11 +1000, Jim Lemon wrote:
>> > On Mon, Aug 3, 2020 at 8:52 PM Md. Moyazzem Hossain <hossainmm using juniv.edu> wrote:
>> > >
>> > > Hi,
>> > >
>> > > I have a dataset having monthly
>> > > observations (from January to
>> > > December) over a period of time like
>> > > (2000 to 2018). Now, I am trying to
>> > > take an average the value from
>> > > January to July of each year.
>> > >
>> > > The data looks like
>> > > Year    Month  Value
>> > > 2000    1         25
>> > > 2000    2         28
>> > > 2000    3         22
>> > > ....    ......      .....
>> > > 2000    12       26
>> > > 2001     1       27
>> > > .......         ........
>> > > 2018    11       30
>> > > 20118   12      29
>> > >
>> > > Can someone help me in this regard?
>> > >
>> > > Many thanks in advance.
>> >
>> > Hi Md,
>> > One way is to form a subset of your
>> > data, then calculate the means by
>> > year:
>> >
>> > # assume your data is named mddat
>> > mddat2<-mddat[mddat$month < 7,]
>> > jan2jun<-by(mddat2$value,mddat2$year,mean)
>> >
>> > Jim
>>
>> Hi Md,
>>
>> you can also define the period in a new
>> column, and use aggregate like this:
>>
>>         Md <- structure(list(
>>         Year = c(2000L, 2000L, 2000L,
>>         2000L, 2001L, 2018L, 2018L),
>>         Month = c(1L, 2L, 3L, 12L, 1L,
>>         11L, 12L),
>>         Value = c(25L, 28L, 22L, 26L,
>>         27L, 30L, 29L)),
>>         class = "data.frame",
>>         row.names = c(NA, -7L))
>>
>>         Md[Md$Month %in%
>>                 1:6,"Period"] <- "first six months of the year"
>>         Md[Md$Month %in% 7:12,"Period"] <- "last six months of the year"
>>
>>         aggregate(
>>           formula=Value~Year+Period,
>>           data=Md,
>>           FUN=mean)
>>
>> Rasmus
>
>
>