# [R] row sum question

Gabor Grothendieck ggrothendieck at gmail.com
Mon Dec 22 16:48:19 CET 2008

```Assuming DF is a data frame like this:

DF <- data.frame(V1 = c(1, 0, 1, 0), V2 = c(1, 1, 1, 1),
V3 = c(0, 1, 1, 1), V4 = c(0, 0, 0, 1))

# try this:

head(rowSums((rbind(0, cummax(DF)) < rbind(cummax(DF), 0))), -1)

On Sun, Dec 21, 2008 at 8:36 PM, Keun-Hyung Choi <khchoi at sfsu.edu> wrote:
> Dear helpers,
>
>
>
> I'm using R version 2.8.0.
>
> Suppose that I have a small data set like below.
>
> [,1] [,2] [,3] [,4]
>
> a    1    1    0    0
>
> b    0    1    1    0
>
> c    1    1    1    0
>
> d    0    1    1    1
>
>
>
> First, I'd like to find row sum of values uniquely present in each row, but
> only sequentially from the top row, meaning that if the value is shown in
> the above row(s) already, the same value in the following row shouldn't be
> added into the sum.
>
> The result should be like this:
>
>
>
> row.sum
>
> [1] 2 1 0 1
>
>
>
> And if a and c were swapped, the row.sum is  3 0 0 1
>
>
>
> Second, I'd like to randomly reorder the rows, and repeat calculating
> row.sum again, for many times less than all combinations possible (4! In
> this case), kind of simulation, and store the results into a matrix.
>
> Thanks.
>
> Keun-Hyung
>
>
>
>
>
>
>
>
>
>
>        [[alternative HTML version deleted]]
>
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> and provide commented, minimal, self-contained, reproducible code.
>

```