# [R] Dividing rows in groups

jim holtman jholtman at gmail.com
Sun Apr 24 18:26:24 CEST 2016

```This will handle all the columns; it assumes the ones you want to start
with are in column 2 through the end:

> library(dplyr)
> df1 <- read.table(text = "ID       A             B
+ 1         1             2
+ 1         0             3
+ 2        5             NA
+ 2         1             3
+ 3         1             4
+ 4         NA           NA
+ 4         0             1
+ 4         3             0
+ 5         2             5
+ 5         7           NA", header = TRUE)
> df2 <- df1 %>%
+         group_by(ID) %>%
+         do({  # now process and indeterinant number of columns
+             result <- .  # get original input
+             for (i in 2:ncol(result)){
+                 result[[i]] <- result[[i]] / sum(result[[i]], na.rm =
TRUE)
+             }
+             result  # return value
+         })
>
> df2
Source: local data frame [10 x 3]
Groups: ID [5]

ID         A     B
(int)     (dbl) (dbl)
1      1 1.0000000   0.4
2      1 0.0000000   0.6
3      2 0.8333333    NA
4      2 0.1666667   1.0
5      3 1.0000000   1.0
6      4        NA    NA
7      4 0.0000000   1.0
8      4 1.0000000   0.0
9      5 0.2222222   1.0
10     5 0.7777778    NA

Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?
Tell me what you want to do, not how you want to do it.

On Sun, Apr 24, 2016 at 12:02 PM, Saba Sehrish <sabasehrish at yahoo.com>
wrote:

> Hi Jim
>
> Thanks a lot. Its really helpful but actually I have around 10,000 columns
> & 8000 rows. I simply want to get the weight of each observation in a group
> (group is identified by ID). Therefore, I am looking for an easy way to
> divide each observation in a row with the sum of all values in its group.
>
> How can I apply this on such a huge data set?
>
> Regards
> Saba
>
>
>
> Sent from Yahoo Mail on Android
> <https://overview.mail.yahoo.com/mobile/?.src=Android>
>
> On Mon, 25 Apr, 2016 at 3:38 AM, jim holtman
> <jholtman at gmail.com> wrote:
> You can use 'dplyr':
>
> > library(dplyr)
> > df1 <- read.table(text = "ID       A             B
> + 1         1             2
> + 1         0             3
> + 2        5             NA
> + 2         1             3
> + 3         1             4
> + 4         NA           NA
> + 4         0             1
> + 4         3             0
> + 5         2             5
> + 5         7           NA", header = TRUE)
> > df2 <- df1 %>%
> +         group_by(ID) %>%
> +         mutate(new_A = A / sum(A, na.rm = TRUE)
> +             , new_B = B / sum(B, na.rm = TRUE)
> +             )
> >
> > df2
> Source: local data frame [10 x 5]
> Groups: ID [5]
>
>       ID     A     B     new_A new_B
>    (int) (int) (int)     (dbl) (dbl)
> 1      1     1     2 1.0000000   0.4
> 2      1     0     3 0.0000000   0.6
> 3      2     5    NA 0.8333333    NA
> 4      2     1     3 0.1666667   1.0
> 5      3     1     4 1.0000000   1.0
> 6      4    NA    NA        NA    NA
> 7      4     0     1 0.0000000   1.0
> 8      4     3     0 1.0000000   0.0
> 9      5     2     5 0.2222222   1.0
> 10     5     7    NA 0.7777778    NA
>
>
>
> Jim Holtman
> Data Munger Guru
>
> What is the problem that you are trying to solve?
> Tell me what you want to do, not how you want to do it.
>
> On Sun, Apr 24, 2016 at 12:46 AM, Saba Sehrish via R-help <
> r-help at r-project.org> wrote:
>
>> Hi
>>
>>
>> I have two data frames as shown below (second one is obtained by
>> aggregating rows of similar IDs in df1.). They both have similar number of
>> columns but rows of df2 are lesser than rows of df1.
>>
>>
>> df1:
>> ID       A             B
>> 1         1             2
>> 1         0             3
>> 2        5             NA
>> 2         1             3
>> 3         1             4
>> 4         NA           NA
>> 4         0             1
>> 4         3             0
>> 5         2             5
>> 5         7           NA
>>
>>
>> df2:
>> ID       A          B
>> 1         1          5
>> 2         6          3
>> 3         1          4
>> 4         3          1
>> 5        9          5
>>
>> Now, to obtain weight of each value of df1, I want to divide each row of
>> df1 by the row of df2 having similar ID. What I want is as below:
>>
>> ID    A    B
>> 1    1    0.4
>> 1    0    0.6
>> 2    0.83  NA
>> 2    0.17  1
>> 3    1     4
>> 4    NA    NA
>> 4    0     1
>> 4    1     0
>> 5    0.22  1
>> 5    0.78  NA
>>
>>
>> Kindly guide me in this regard.
>>
>> Thanks
>> Saba
>>
>> ______________________________________________
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