excel - Using R to reformat data from cross-tab to one-datum-per-line format -

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i'm using r pull in data through api , merge of single table, write csv file. graph in tableau, however, need prepare data using reformatting tool excel cross-tablulated format format each line contains 1 piece of data. example, taking format:

id,gender,school,math,english,science 1,m,west,90,80,70 2,f,south,50,50,50

to:

id,gender,school,subject,score 1,m,west,math,90 1,m,west,english,80 1,m,west,science,70 2,f,south,math,50 2,f,south,english,50 2,f,south,science,50

are there existing tools in r or in r library allow me this, or provide starting point? trying automate preparation of data tableau need run single script formatted properly, , remove manual excel step if possible.

in r , several other programs, process referred "reshaping" data. in fact, tableau page that linked to speaks of "excel reshaper plugin".

in base r, there few functions reshape data, such (notorious) reshape() function takes panel data wide form long form, , stack() creates skinny stacks of data.

the "reshape2" package seems more popular such data transformations, though. here's example of "melting" sample data, i've stored in data.frame named "mydf":

library(reshape2) melt(mydf, id.vars=c("id", "gender", "school"),       value.name="score", variable.name="subject") #   id gender school subject score # 1  1      m   west    math    90 # 2  2      f  south    math    50 # 3  1      m   west english    80 # 4  2      f  south english    50 # 5  1      m   west science    70 # 6  2      f  south science    50

for example, base r's reshape() isn't appropriate, stack() is. here, i've stacked last 3 columns:

stack(mydf[4:6]) #   values     ind # 1     90    math # 2     50    math # 3     80 english # 4     50 english # 5     70 science # 6     50 science

to data.frame looking for, cbind first 3 columns above output.

for reference, hadley wickham's tidy data paper entry point thinking how structure of data might facilitate further processing , visualization.


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