Hi there, I am stuck trying to solve what should be a fairly easy problem. I have a data frame that essentially consists of (ID, time as seqMonth, variable, value) and i want to find the regression coefficient of value vs time for each combination of ID and Variable. I have tried several approaches and none of them seems to work as i expected. For example, i have tried:
theSplit<-split(theTestLineal, list(as.factor(theTestLineal $ids), as.factor(theTestLineal $variable))) I can then use lm(value~seqMonth,data=zongSplit[[1]]) ... lm(value~seqMonth,data=zongSplit[[4]]) that works well, (it fails for some combinations of ID and variable where there is one datapoint) however when i try to use an lapply: lapply(zongSplit,function(x)lm(value~seqMonth,data=x,na.action=na.exclude)) it fails, with error message: Error in lm.fit(x, y, offset = offset, singular.ok = singular.ok, ...) : 0 (non-NA) cases I have tried to change the na.action with no success (na.pass, na.fail, na.exclude... all give the same error message) I have also tried to follow the approach suggested by Charles Sharpsteen (http://www.mail-archive.com/r-help@r-project.org/msg74759.html) with similar results. The code is as follows: theModels <- by( theTestLineal, list( theTestLineal$ids, zongTestLineal$variable), function( dataSlice ){ linMod <- lm( value ~ seqMonth, data = dataSlice ) # Slope and intercept may be recovered from the output of the coef() function: intercept <- coef( linMod )[1] slope <- coef( linMod )[2] # The R-Squared value is returned by the summary() function: rsq <- summary( linMod )[[ 'r.squared' ]] # The summary function also provides statistics for the F-distribution, # extract them, reformat as a list, rename and feed to pf() using do.call() # in order to get the p-value: fStats <- as.list( summary( linMod )[[ 'fstatistic' ]] ) names( fStats ) <- c( 'q', 'df1', 'df2' ) fStats[[ 'lower.tail' ]] <- FALSE pVal <- do.call( pf, fStats ) return(data.frame( slope, intercept, rsq, pVal )) }) Any help will be appreciated! [[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.
