[R] How to reshape wide format data.frame to long format?

[Abhijit Dasgupta]

I would think that the following code should work:

newcodesM = reshape(codesM, id=1)

If other variables in the data.frame are factors, reshape thinks all of them are ID variables and tries to use all of them as "keys". Specifying the id variable you want to keep (I used id=1 since "key" is in the 1st column) will probably solve the issue. 

Abhijit

On Jan 20, 2011, at 10:51 AM, Fredrik Karlsson wrote:

> Dear list,
> 
> I need to convert this data.frame
> 
>> names(codesM)
> [1] "key"        "AMR.pa1.M"  "AMR.pa2.M"  "AMR.pa3.M"  "AMR.pa4.M"
> [6] "AMR.pa5.M"  "AMR.pa6.M"  "AMR.pa7.M"  "AMR.pa8.M"  "AMR.pa9.M"
> [11] "AMR.pa10.M" "AMR.ta1.M"  "AMR.ta2.M"  "AMR.ta3.M"  "AMR.ta4.M"
> [16] "AMR.ta5.M"  "AMR.ta6.M"  "AMR.ta7.M"  "AMR.ta8.M"  "AMR.ta9.M"
> [21] "AMR.ta10.M" "AMR.ka1.M"  "AMR.ka2.M"  "AMR.ka3.M"  "AMR.ka4.M"
> [26] "AMR.ka5.M"  "AMR.ka6.M"  "AMR.ka7.M"  "AMR.ka8.M"  "AMR.ka9.M"
> [31] "AMR.ka10.M" "SMR.pa1.M"  "SMR.pa2.M"  "SMR.pa3.M"  "SMR.pa4.M"
> [36] "SMR.pa5.M"  "SMR.pa6.M"  "SMR.pa7.M"  "SMR.pa8.M"  "SMR.pa9.M"
> [41] "SMR.pa10.M" "SMR.ta1.M"  "SMR.ta2.M"  "SMR.ta3.M"  "SMR.ta4.M"
> [46] "SMR.ta5.M"  "SMR.ta6.M"  "SMR.ta7.M"  "SMR.ta8.M"  "SMR.ta9.M"
> [51] "SMR.ta10.M" "SMR.ka1.M"  "SMR.ka2.M"  "SMR.ka3.M"  "SMR.ka4.M"
> [56] "SMR.ka5.M"  "SMR.ka6.M"  "SMR.ka7.M"  "SMR.ka8.M"  "SMR.ka9.M"
> [61] "SMR.ka10.M"
>> dim(codesM)
> [1] 42 61
> 
> into a 3 x  2501 data.frame where the "key" variable is kept, the
> values in columns 2-61 above is inserted into a "values" column and
> the name of the column is inserted in a third column ("variable"
> perhaps).
> 
> Like
> 
> key                         variable              value
> POSTOFF_1_1    AMR.pa1.M       5
> POSTOFF_1_1    AMR.pa2.M       3
> ....
> 
> I think I should be able to do this using the "reshape" function, but
> I cannot get it to work. I think I need some help to understand
> this...
> 
> 
> (If I could split the "variable" into three separate columns splitting
> by ".", that would be even better.)
> 
> I appreciate all the help I could get.
> 
> /Fredrik
> 
> -- 
> "Life is like a trumpet - if you don't put anything into it, you don't
> get anything out of it."
> 
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