[R] How to manipulate tables

[William Dunlap]

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of James Rome
> Sent: Saturday, December 26, 2009 11:03 AM
> To: r-help at r-project.org
> Subject: [R] How to manipulate tables
> 
> I am sorry to be bothering the list so much.
> 
> I made a table of counts of flight arrivals by hour:
> cnts=tapply(Arrival4,list(Hour),table). There are up to 15 
> arrivals in a
> bin.
> > cnts
> $`0`
> 
>  1  2  3  4  5  6  7  8  9 10 13
>  1  2  5  9  2  7  5  4  2  4  1
> 
> $`1`
> 
> 1 2 3 4
> 3 2 2 1
> 
> $`2`
> 
> 1 3
> 2 2
> .  . .
> 
> My first problem is how to get this table filled in with the 0 slots.
> E.g., I want
> $`0`
> 
>  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15
>  1  2  5  9  2  7  5  4  2  4   0   0   1   0   0
> 
> for all 24 hours. The elements of the tables are lists, but I do not
> seem to be able to extract the names of each list, which I think would
> allow this manipulation.

Let's make a fake dataset to demonstrate things more easily.
  set.seed(1)
  data <- data.frame(Arrival4=rpois(50, 4)+1,
                     Hour=sample(0:4, replace=TRUE, size=50))
Your tapply(,FUN=table) approach with this data gives
  > with(data, tapply(Arrival4,list(Hour),table))
  $`0`

  3 4 6 8 
  2 2 1 1 

  $`1`

  3 4 5 6 7 8 
  3 2 2 3 1 3 
  ... 2 more one dimensional tables, `3` and `4` ...

I prefer making a two dimensional table so the rows and
columns have common meanings
  > tab <- with(data, table(Hour, Arrival4))
  > tab
      Arrival4
  Hour 1 2 3 4 5 6 7 8 11
     0 0 0 2 2 0 1 0 1  0
     1 0 0 3 2 2 3 1 3  0
     2 0 2 0 2 3 3 0 0  0
     3 0 0 0 0 2 4 4 0  1
     4 1 0 2 3 1 2 0 0  0
  > tab[2,] # 2nd row (Hour==1)
   1  2  3  4  5  6  7  8 11 
   0  0  3  2  2  3  1  3  0
  > tab["1",] # would give the same as tab[2,]

But this is missing columns for Arrival4 in c(10,12,13,14,15).
If you make Arrival4 a factor with levels 1:15 the table will
include entries for each level.  In the following we don't actually
change Arrival4 itself, but create a factor using its data
when we call table().
  > tab <- with(data, table(Hour,
Arrival4=factor(Arrival4,levels=1:15)))
  > tab
      Arrival4
  Hour 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
     0 0 0 2 2 0 1 0 1 0  0  0  0  0  0  0
     1 0 0 3 2 2 3 1 3 0  0  0  0  0  0  0
     2 0 2 0 2 3 3 0 0 0  0  0  0  0  0  0
     3 0 0 0 0 2 4 4 0 0  0  1  0  0  0  0
     4 1 0 2 3 1 2 0 0 0  0  0  0  0  0  0
  > tab[2,] # 2nd row (Hour==1)
   1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 
   0  0  3  2  2  3  1  3  0  0  0  0  0  0  0  

If you have no data for certain hours, you may have
to use the same technique for Hour.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com 
 
> My second problem is that I want to compute probability 
> distributions. I
> have
> lambda
>           0           1           2           4           5          
> 6           7
> 0.199190283 0.013765182 0.006477733 0.017813765 0.093117409 
> 0.160323887
> 0.401619433
>           8           9          10          11          12         
> 13          14
> 0.191093117 0.177327935 0.318218623 0.404858300 0.463157895 
> 0.495546559
> 0.435627530
>          15          16          17          18          19         
> 20          21
> 0.418623482 0.307692308 0.405668016 0.484210526 0.580566802 
> 0.585425101
> 0.519028340
>          22          23
> 0.556275304 0.503643725
> 
> and I need to calculate lambda**cnts for each bin, and each hour. I am
> also unsure of how to do this.
> 
> Thanks in advance kind people on this list
> Jim Rome
> 
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