Hi ST,
You could try this:
library(plyr)
set.seed(25)
mydf<- data.frame(subid=rep(1:5,each=3),Col=sample(c(0:5,NA),15,replace=TRUE))
retsample <- function(df, Column,size) {
set.seed(1234)
mysel <- ddply(df, .(subid),function(x)
summarize(x,missing=sum(is.na(x[[Column]])|x[[Column]]==0)))
myids<- mysel[mysel$missing==0,1]
sample_regular<- subset(df,subid%in% sample(myids,size,replace=TRUE))
return(sample_regular)
}
retsample(mydf,"Col",5)
# subid Col
#1 1 2
#2 1 4
#3 1 1
#10 4 1
#11 4 2
#12 4 2
A.K.
>Thanks David for the tip. I dont think I still have this working for a
function that i am writing. Say col, subid are column names in my
dataframe >mydf. My calling function is retsample(mydf,"Col",5)
>This below function fails in ddply call. In this call I am counting
how many nulls or zeros exist for that colum that I am passing. I get
"Error in >eval(expr, envir, enclos) : object 'myCol' not found"
>
>#Get appropriate random sample to print for variable col from dataframe df,
>that has 0 missing values
>retsample <- function(df,x,size ) {
> set.seed(1234)
> myCol <- df[[x]]
> mysel <- ddply(df,c("subid"),summarise,missing=sum(is.na(myCol)|
myCol==0))
> #select subjects with no missing values
> myids <- mysel[mysel$missing==0,1]
> sample_regular <- subset(df,subid %in% sample(myids, size=size))
> return(sample_regular)
>}
>
>Thank You for your assistance.
>-ST
----- Original Message -----
From: arun <smartpink...@yahoo.com>
To: R help <r-help@r-project.org>
Cc:
Sent: Tuesday, April 30, 2013 9:00 AM
Subject: Re: R Function to extract columnNames
Hi,
May be this helps:
funcName<- function(df1, x){
whatCol=df1[[x]]
print("Got it")
print(whatCol)
}
funcName(df,"ColA")
#[1] "Got it"
#[1] 1 2 3 4 5
funcName(df,"ColB")
#[1] "Got it"
#[1] A B C D E
#Levels: A B C D E
A.K.
>I am trying to extract the 2nd column from a dataframe using a function
called funcName. Note this is an example that I need cos I am using it
to >read the values I pass into a function call - these passed values
represent dataframe column names. I am trying to use this concept for a
vary large >dataframe with 100+ columns.
>
>ColA <- c(1,2,3,4,5)
>ColB <- c("A","B","C","D","E")
>df <- data.frame(ColA,ColB)
>
>funcName <- function(x) {
> whatCol = paste("df",x,sep="$")
>print("Got it",whatCol)
>}
>
>funcName("ColA")
>
>Please advise, since this code is not working. Thanks in advance.
>
>-ST
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