[R] help with data layout

Erik Iverson iverson at biostat.wisc.edu
Thu Jul 17 18:19:34 CEST 2008

Iain Gallagher wrote:
> Hello list
> I have been given some Excel sheets with data laid like this:
> Col1    Col2 A         3 2 3 B         4 5 4 C         1 4 3
> I was hoping to import this into R as a csv and then get the mean and
> SD for each letter in column 1.
> Could someone give me some guidance on best to approach this?

Sure.  Reading in Excel sheets can be done at least a few ways, see the 
R Data Import/Export manual on CRAN.  The only way I have done it is to 
save the Excel sheet as a CSV file, and then use read.csv in R to get a 
data.frame.  One note here is that sometimes the Excel sheet has 
'missing' cells where someone has inserted blanks.  These may get 
written out to the CSV file, you'll have to check.  For example, I've 
seen an Excel sheet with something like 10 rows of data that outputs 
about 100 to the CSV file, mostly all missing.

Anyway, once you have the data.frame, I'd use na.locf from the zoo 
package to 'fill' in the missing Col1 values, and then use an R function 
such as ave, tapply, aggregate, or by to do whatever you'd like.

> Thanks
> Iain
> [[alternative HTML version deleted]]
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