Custom function in R

Question

I have created some simple functions in R that take data and return variables. I'd appreciate instruction on taking this to another level using the code below as illustration: There's a data frame 'df' which contains variables DOFW, CDFME (there are others, but two will suffice for this example. I'd like to pass to the function the name of the variable and have it build the barplot. Basically I want to create a function that performs the actions from z<- through abline and call that function for each variable. Thank you.

df<-data.frame(y.train,x.train) z<-ddply(df,~DOFW,summarise,median=median(PCTCHG)) row.names(z)<-z$DOFW z$DOFW<-NULL barplot(t(as.matrix(z)),main="Median Return by DOFW",xlab="DOFW") abline(h=median(y.train)) z<-ddply(df,~CDFME,summarise,median=median(PCTCHG)) row.names(z)<-z$CDFME z$CDFME<-NULL barplot(t(as.matrix(z)),main="Median Return by CDFME",xlab="CDFME") abline(h=median(y.train))

The short answer is that if you want a column name to be a variable, you'll need to use [ instead of $ and adjust your ddply calls to not use a formula or to build the correct formula with paste and expression. The long answer is to read part of Hadley's Advanced R book, paying special attention to the "Non-Standard Evaluation in Subset" section. — Gregor Thomas
– Gregor Thomas, Commented Jul 11, 2014 at 20:51

MrFlick · Accepted Answer · 2014-07-12 02:06:24Z

Actually you don't really need non-standard evaluation since ddply allows you to pass a string for the variable name rather than a formula. Here's how you could do that.

#sample data dd<-data.frame(a=rep(1:5, 2), b=2:11, c=runif(10)) #define function library(plyr) myplot<-function(coln) { z<-ddply(dd, coln, summarise, median=median(c)) barplot(z[,2], main=paste("Median Return By", coln)) abline(h=median(dd$c)) } #make plots myplot("a") myplot("b")

and the easiest way to get the names of the columns as a character vector is names(dd).

Collectives™ on Stack Overflow

Custom function in R

1 Answer 1

Comments

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Related