CODEWITHSUNDEEP
rdataframe
Victor Van Hee
Victor Van Hee

Reputation: 9919

How to convert a table to a data frame

I have a table in R that has str() of this:

 table [1:3, 1:4] 0.166 0.319 0.457 0.261 0.248 ...
 - attr(*, "dimnames")=List of 2
  ..$ x: chr [1:3] "Metro >=1 million" "Metro <1 million" "Non-Metro Counties"
  ..$ y: chr [1:4] "q1" "q2" "q3" "q4"

And looks like this when I print it:

                    y
x                           q1        q2        q3        q4
  Metro >=1 million  0.1663567 0.2612212 0.2670441 0.3053781
  Metro <1 million   0.3192857 0.2480012 0.2341030 0.1986102
  Non-Metro Counties 0.4570341 0.2044960 0.2121102 0.1263597

I want to get rid of the x and y and convert it to a data frame that looks exactly the same as the above (three rows, four columns), but without the x or y. If I use as.data.frame(mytable), instead I get this:

                    x  y      Freq
1   Metro >=1 million q1 0.1663567
2    Metro <1 million q1 0.3192857
3  Non-Metro Counties q1 0.4570341
4   Metro >=1 million q2 0.2612212
5    Metro <1 million q2 0.2480012
6  Non-Metro Counties q2 0.2044960
7   Metro >=1 million q3 0.2670441
8    Metro <1 million q3 0.2341030
9  Non-Metro Counties q3 0.2121102
10  Metro >=1 million q4 0.3053781
11   Metro <1 million q4 0.1986102
12 Non-Metro Counties q4 0.1263597

I probably fundamentally do not understand how tables relate to data frames.

Upvotes: 222

Views: 340077

Answers (4)

Victor Van Hee
Victor Van Hee

Reputation: 9919

I figured it out already:

as.data.frame.matrix(mytable)

does what I need -- apparently, the table needs to somehow be converted to a matrix in order to be appropriately translated into a data frame. I found more details on this as.data.frame.matrix() function for contingency tables at the Computational Ecology blog.

Upvotes: 418

BLT
BLT

Reputation: 2552

While the results vary in this case because the column names are numbers, another way I've used is data.frame(rbind(mytable)). Using the example from @X.X:

> freq_t = table(cyl = mtcars$cyl, gear = mtcars$gear)

> freq_t
   gear
cyl  3  4  5
  4  1  8  2
  6  2  4  1
  8 12  0  2

> data.frame(rbind(freq_t))
  X3 X4 X5
4  1  8  2
6  2  4  1
8 12  0  2

If the column names do not start with numbers, the X won't get added to the front of them.

Upvotes: 26

Ben
Ben

Reputation: 42343

If you are using the tidyverse, you can use

as_data_frame(table(myvector))

to get a tibble (i.e. a data frame with some minor variations from the base class)

Upvotes: 9

X.X
X.X

Reputation: 981

Short answer: using as.data.frame.matrix(mytable), as @Victor Van Hee suggested.

Long answer: as.data.frame(mytable) may not work on contingency tables generated by table() function, even if is.matrix(your_table) returns TRUE. It will still melt you table into the factor1 factor2 factori counts format.

Example:

> freq_t = table(cyl = mtcars$cyl, gear = mtcars$gear)

> freq_t
   gear
cyl  3  4  5
  4  1  8  2
  6  2  4  1
  8 12  0  2

> is.matrix(freq_t)
[1] TRUE

> as.data.frame(freq_t)
  cyl gear Freq
1   4    3    1
2   6    3    2
3   8    3   12
4   4    4    8
5   6    4    4
6   8    4    0
7   4    5    2
8   6    5    1
9   8    5    2
> as.data.frame.matrix(freq_t)
   3 4 5
4  1 8 2
6  2 4 1
8 12 0 2

Upvotes: 15

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