Re: [R] help with data layout

From: Erik Iverson <iverson_at_biostat.wisc.edu>
Date: Thu, 17 Jul 2008 11:19:34 -0500

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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