Dear R-Helpers: I am using trying to use *ddply* to extract min and max of a particular column in a data.frame. I am using two different forms of the function:
## var_name_to_split is a string -- something like "var1" which is the name of a column in data.frame ddply( df, .(as.name(var_name_to_split)), function(x) c(min(x[ , 3] , max(x[ , 3]))) ## fails with an error - case 1 ddply( df, var_name_to_split , function(x) c(min(x[ , 3] , max(x[ , 3]))) ## works fine - case 2 I can't understand why I get the error in case 1. Can someone help me please? Thank you in advance. S. ---------- Here is the reproducible code: https://gist.github.com/730069 Here is sample data: structure(list(g10 = c(1L, 1L, 1L, 10L, 10L, 10L), l1 = c(0.410077661080032, 0.607497980054711, 0.640488621149069, -1.47837849145189, -1.48199933642397, -1.42815840788069), d1 = c(0.917769870675383, 0.959256755797054, 0.772928570498006, 0.473545787883884, 0.590580940273922, 0.0448629265021484 ), l13 = c(0.0803696045647364, -0.291741079837731, -0.00191015929550312, 0.295889063381279, 0.615383505686296, 0.71991154637985), d13 = c(-1.40821713632015, -1.27501365601403, -1.41150703235157, 0.708943640186729, 0.276034890463749, 0.663383934998686)), .Names = c("g10", "l1", "d1", "l13", "d13" ), row.names = c(1L, 2L, 3L, 1758L, 1759L, 1760L), class = "data.frame") ----------- If some one doesn't want to open github - here is the code ## Doesn't work # grp -- name of a column of the the data.frame df # function call is -- getMinMax1( df1 , grp = "var1") getMinMax1 <-function(df, grp){ dfret <- ddply( df , .(as.name(grp)), ## I am using as.name(grp), source of error function(x){ minmax <- c(mix(x[ , 3]), max(x[ ,3])) return(minmax) } ) return(dfret) } ## Works fine # grp -- name of a column of the the data.frame df # function call is -- getMinMax2( df1 , grp = "var1") getMinMax2 <-function(df, grp){ dfret <- ddply( df , grp, ## using the quoted variable name passed to grp when the fun is called function(x){ minmax <- c(min(x[ , 3]), max(x[ ,3])) return(minmax) } ) return(dfret) } [[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.