How to aggregate data by transect with dplyr in R?

Question

I have a large database which I want to simplify by grouping observations into transects. I have used the following code:

library(dplyr)
AGGDATA<-DATA %>%  
  select(Habitat,Transect,Number,Abundance) %>%
  group_by(Transect) %>%
  mutate(TotalNum = sum(Number),TotalAbund = sum(Abundance))

Sample output for DATA$Abundance looks like this:

  [1]   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0
 [24]   0   0   0   0   0   0   1   0   0   0   0   0   0   0   0   0   0  16   9   6   1   21   5
 [47]  83  32  10   1  24   2  16  85   7   4   0  21   1   7   7   9   4  76   0   1   2   2   1
 [70]   9   2   0   3   6  41   4   3   5   0   0   0   0   0   0   0   0   0   0   0   0   1   0
 [93]   0   0   0   0   0   0   0   0   0  78  14   3   1  10  44   5   0   2   2  31   1   3  18

And sample output for AGGDATA$TotalAbund looks like this:

[1]     1    1    1    1    1    1    1    1    1    1    1    1    1    1    1    1    1    1
[19]    1    1    1    1    1    1    1    1    1    1    1    1    1    1    1    1    1    1
[37]    1    1    1    1  351  351  351  351  351  351  351  351  351  351  351  351  351   351
[55]  351  351  351  351  351  351  175  175  175  175  175  175  175  175  175  175  175   175
[73]  175  175  175  175  175  175  175  175    1    1    1    1    1    1    1    1    1    1

The code has summed DATA$Abundance values for each transect. However, I would like one value per transect rather than one value repeated for each transect observation. I'm still new to this so I hope that makes sense.

Can anyone help? Thanks!!

Answer 1

I would recommend you to use data.table library. It is much faster. In case of you didn't provide a data set, so your solution can look like

library(data.table)
DATA <- data.table(DATA)
AGGDATA <- DATA[, .(TotalNum = sum(Number),TotalAbund = sum(Abundance)), by = Transect]