Example of reading fixed width format data in readr & possible bug

[Bob]

Hi All,

Here's an example of how to use readr's read_fwf function to read data with no delimiters like this:

011f1151

022f2141

031f2243

042 31 3

051m3524

062m5455

071m5344

082m4555

Each variable takes only one column except for the first one, which takes 2. You can specify how wide each variable is using the form below. If you're used to using R's built-in read.fwf function, note that you cannot skip variables by specifying a negative value, but that's easy to work around.

> read_fwf("mydataFWF.txt", 

+          fwf_widths( c(2, 1, 1, 1, 1, 1, 1) ) )

  X1 X2 X3 X4 X5 X6 X7

1  1  1  f  1  1  5  1

2  2  2  f  2  1  4  1

3  3  1  f  2  2  4  3

4  4  2     3  1 NA  3

5  5  1  m  3  5  2  4

6  6  2  m  5  4  5  5

7  7  1  m  5  3  4  4

8  8  2  m  4  5  5  5

That's handy, but if you get a single width wrong, all the following variables will be wrong too. So it's safer to specify the starting and ending columns for each variable like this:

read_fwf("mydataFWF.txt", 

         fwf_positions( c(1,3,4,5,6,7,8),

                        c(2,3,4,5,6,7,8)))

The help file says you can specify variable names using the col_names argument, but either there's a bug or I'm missing something about how to use it:

> read_fwf("mydataFWF.txt", 

+          fwf_widths( c(2, 1, 1, 1, 1, 1, 1) ),

+          col_names = c("id","workshop","gender","q1","q2","q3","q4") )

Error in read_fwf("mydataFWF.txt", fwf_widths(c(2, 1, 1, 1, 1, 1, 1)),  : 

  unused argument (col_names = c("id", "workshop", "gender", "q1", "q2", "q3", "q4"))

I get the same message using fwf_widths.

Cheers,

Bob

[Hadley Wickham]

Hi Bob,

col_names() is an argument of fwf_widths()/fwf_positions(), not read_fwf()

Hadley

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[Bob]

Thanks!  OK, so here are the col_names working in my example:

> read_fwf("mydataFWF.txt", 

+          fwf_positions( 

+            c(1,3,4,5,6,7,8),

+            c(2,3,4,5,6,7,8),

+            col_names = c("id","workshop","gender","q1","q2","q3","q4") ))

  id workshop gender q1 q2 q3 q4

1  1        1      f  1  1  5  1

2  2        2      f  2  1  4  1

3  3        1      f  2  2  4  3

4  4        2         3  1 NA  3

5  5        1      m  3  5  2  4

6  6        2      m  5  4  5  5

7  7        1      m  5  3  4  4

8  8        2      m  4  5  5  5