Accessing data from output R program - r

Question

I have an output generated by the cuts functions which is the one below...lets call this ouput 'data'.
cuts: [20,25)
Time Kilometres
21 20 7.3
22 21 8.4
23 22 9.5
24 23 10.6
25 24 11.7
------------------------------------------------------------
cuts: [25,30)
Time Kilometres
26 25 12.8
27 26 13.9
28 27 15.0
29 28 16.1
30 29 17.2
------------------------------------------------------------
cuts: [30,35)
Time Kilometres
31 30 18.3
32 31 19.4
33 32 20.5
34 33 21.6
35 34 22.7
How could I access the data in each cut..like get the kilometres data from cuts:[20,25]..etc I tried doing data$Kilometres...but this does not work...So I basically want a new data frame where I could use the kilometres data seperately for each cut

Answer 1

The output of by here is a list, so you can use basic list indexing, either by number or name. Using the data from your question from a few hours ago, and the answer from Matthew Lundberg, we can index as follows:
> x[[1]]
Time Velocity
1 0.0 0.00
2 1.5 1.21
3 3.0 1.26
4 4.5 1.31
> x[["[6,12)"]]
Time Velocity
5 6.0 1.36
6 7.5 1.41
7 9.0 1.46
8 10.5 1.51
You can review the structure of objects in R by using str. This is usually useful to help you decide how you can extract certain information. Here's str(x):
> str(x)
List of 7
$ [0,6) :Classes ‘AsIs’ and 'data.frame': 4 obs. of 2 variables:
..$ Time : num [1:4] 0 1.5 3 4.5
..$ Velocity: num [1:4] 0 1.21 1.26 1.31
$ [6,12) :Classes ‘AsIs’ and 'data.frame': 4 obs. of 2 variables:
..$ Time : num [1:4] 6 7.5 9 10.5
..$ Velocity: num [1:4] 1.36 1.41 1.46 1.51
$ [12,18):Classes ‘AsIs’ and 'data.frame': 6 obs. of 2 variables:
..$ Time : num [1:6] 12 13 14 15 16 17
..$ Velocity: num [1:6] 1.56 1.61 1.66 1.71 1.76 1.81
$ [18,24):Classes ‘AsIs’ and 'data.frame': 5 obs. of 2 variables:
..$ Time : num [1:5] 18 19 20 21 22.5
..$ Velocity: num [1:5] 1.86 1.91 1.96 2.01 2.06
$ [24,30):Classes ‘AsIs’ and 'data.frame': 4 obs. of 2 variables:
..$ Time : num [1:4] 24 25.5 27 28.5
..$ Velocity: num [1:4] 2.11 2.16 2.21 2.26
$ [30,36):Classes ‘AsIs’ and 'data.frame': 4 obs. of 2 variables:
..$ Time : num [1:4] 30 31.5 33 34.5
..$ Velocity: num [1:4] 2.31 2.36 2.41 2.42
$ [36,42):Classes ‘AsIs’ and 'data.frame': 1 obs. of 2 variables:
..$ Time : num 36
..$ Velocity: num 2.43
- attr(*, "dim")= int 7
- attr(*, "dimnames")=List of 1
..$ cuts: chr [1:7] "[0,6)" "[6,12)" "[12,18)" "[18,24)" ...
- attr(*, "call")= language by.data.frame(data = mydf, INDICES = cuts, FUN = I)
- attr(*, "class")= chr "by"
From this we can see that we have a named list of seven items, and each list contains a data.frame. Thus, if we wanted a vector of just the "Velocity" variable (second column) for the third interval, we would use something like:
> x[[3]][[2]]
[1] 1.56 1.61 1.66 1.71 1.76 1.81