If the argument to the function you give in the 'by' call were 'z' instead of 'x', then it would have been easier to see what was wrong.
You are using 'xx' inside the function rather than 'x'. I think you want something like: function(z) {cor(z$Data1.MEAN, z$Data2.MEAN)} Pat On 27/07/2014 08:04, Mateusz Kędzior wrote:
Hello all, I strongly believe, that my issue is quite easy to resolve. However, I have no idea how to find/debug what is wrong and I would blame myself for insufficient knowledge about data tables and some useful functions in R! as apply, sapply, lapply. My question is as follows: I would like to display correlation coefficients in a table (ideally - with p-value, but below there's only Pearson correlation coefficients). However, my code produces exactly the same values for each period (so something is obviously wrong). Could you give me any advice: #first of all, I read my data table from CSV file: imported <- read.table (file="/home/someone/data_for_R.csv", header=TRUE, sep='\t', quote='"\'', dec=',', fill=FALSE, comment.char="#", na.strings = "NA", nrows = -1, skip = 0, check.names = TRUE, strip.white = FALSE, blank.lines.skip = TRUE) # Typing: class(imported[["Period"]]) produces: # [1] "factor" #Typing: levels(imported[["Period"]]) produces: # [1] "Summer 2010" "Summer 2011" "Winter 2010" "Winter 2011" "Winter 2012" xx <- imported[c("Period","Data1.MEAN","Data2.MEAN")] result <- by(xx, xx$Period, function(x) {cor(xx$Data1.MEAN, xx$Data2.MEAN)}) result.dataframe <- as.data.frame(as.matrix(result)) result.dataframe$C <- rownames(result) Best regards, Mateusz [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
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