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I have the following data frame
dat <- data.frame(x=c(1,2,3,3,2,1), y=c(3,4,4,5,2,5))
Now I would like to get a third column dividing the y row value by the aggregated y values (based on the unique values in column x). So, then I get row 1 as following: 1,3,0.375; 0.375 has been calculated as 3 / (5+3).
I'm relatively new to R and I hope you can help me. Thank you!
700
Syntax: mutate(new-col-name = rowSums(.)) The rowSums() method is used to calculate the sum of each row and then append the value at the end of each row under the new column name specified. The argument . is used to apply the function over all the cells of the data frame. Syntax: rowSums(.)
To divide each column by a particular column, we can use division sign (/). For example, if we have a data frame called df that contains three columns say x, y, and z then we can divide all the columns by column z using the command df/df[,3].
First of all, create a data frame. Then, using plus sign (+) to add two rows and store the addition in one of the rows. After that, remove the row that is not required by subsetting with single square brackets.
There are various ways of solving this, here's one
with(dat, ave(y, x, FUN = function(x) x/sum(x)))
## [1] 0.3750000 0.6666667 0.4444444 0.5555556 0.3333333 0.6250000
Here's another possibility
library(data.table)
setDT(dat)[, z := y/sum(y), by = x]
dat
# x y z
# 1: 1 3 0.3750000
# 2: 2 4 0.6666667
# 3: 3 4 0.4444444
# 4: 3 5 0.5555556
# 5: 2 2 0.3333333
# 6: 1 5 0.6250000
Here's a third one
library(dplyr)
dat %>%
group_by(x) %>%
mutate(z = y/sum(y))
# Source: local data frame [6 x 3]
# Groups: x
#
# x y z
# 1 1 3 0.3750000
# 2 2 4 0.6666667
# 3 3 4 0.4444444
# 4 3 5 0.5555556
# 5 2 2 0.3333333
# 6 1 5 0.6250000
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