CODEWITHSUNDEEP
raggregate
dainys
dainys

Reputation: 197

How properly sum variable according to date and save result in a separate data frame in R

I have data

bywells <-
structure(list(Well_N = structure(c(1L, 1L, 1L, 1L, 1L, 2L, 2L, 
2L, 2L), .Label = c("KRT3", "KRT4"), class = "factor"), Date_m = structure(c(16251, 
16281, 16312, 16343, 16373, 16312, 16343, 16373, 16404), class = "Date"), 
    QOM = c(132, 36, 39, 211, 45, 108, 161, 30, 31
    )), class = "data.frame", row.names = c(NA, -9L), .Names = c("Well_N", 
"Date_m", "QOM"))

and would like to sum variable QOM monthly and get result like

       Date_m QOM
1  2014-06-30 132
2  2014-07-30  36
3  2014-08-30 147
4  2014-09-30 372
6  2014-10-30  75
7  2014-11-30  31

Whats the proper procedure to extract unique dates and get sum of QOM according to date?

EDIT: Thanks, folks. Actually both answers are perfect, but I marked as accepted the one with less points to increase karma. Thanks once more.

Upvotes: 0

Views: 81

Answers (3)

chee.work.stuff
chee.work.stuff

Reputation: 326

using plyr

library(plyr)
summarize(group_by(bywells, Date_m),QOM=sum(QOM))

or base tapply

tapply(bywells$QOM, bywells$Date_m, sum)

Upvotes: 2

akrun
akrun

Reputation: 887118

Using data.table

library(data.table)
setDT(bywells)[, list(QOM=sum(QOM)), by=Date_m]
#       Date_m QOM
#1: 2014-06-30 132
#2: 2014-07-30  36
#3: 2014-08-30 147
#4: 2014-09-30 372
#5: 2014-10-30  75
#6: 2014-11-30  31

Or using aggregate from base R

aggregate(QOM~Date_m, bywells, sum)

Upvotes: 3

kohske
kohske

Reputation: 66842

There are many many ways, and dplyr package is one option:

library(dplyr)
bywells %>% group_by(Date_m) %>% summarize(QOM = sum(QOM))

Upvotes: 3

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